```

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM N-Q

                   QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS
    OF REGISTERED MANAGEMENT INVESTMENT COMPANY

  Investment Company Act file number 811-01835

                         Pioneer Series Trust XI
               (Exact name of registrant as specified in charter)

                       60 State Street, Boston, MA 02109
              (Address of principal executive offices) (ZIP code)

            Terrence J. Cullen, Pioneer Investment Management, Inc.,
                       60 State Street, Boston, MA 02109
                    (Name and address of agent for service)

Registrant's telephone number, including area code:  (617) 742-7825

Date of fiscal year end:  December 31

Date of reporting period:  March 31, 2017

Form N-Q is to be used by management investment companies, other than small
business investment companies registered on Form N-5 (239.24 and 274.5 of this
chapter), to file reports with the Commission, not later than 60 days after
close of the first and third fiscal quarters, pursuant to Rule 30b1-5 under
the Investment Company Act of 1940 (17 CFR 270.30b1-5).  The Commission may
use the information provided on Form N-Q in its regulatory, disclosure review,
inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-Q,
and the Commission will make this information public. A registrant is not
required to respond to the collection of information contained in Form N-Q
unless the Form displays a currently valid Office of Management and Budget
("OMB") control number. Please direct comments concerning the accuracy of the
information collection burden estimate and any suggestions for reducing the
burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW,
Washington, DC 20549-0609.  The OMB has reviewed this collection of information
under the clearance requirements of 44 U.S.C. ss. 3507.

<PAGE>
ITEM 1. Schedule of Investments.

File the schedules as of the close of the reporting period as set forth in
ss. 210.12-12  12-14 of Regulation S-X [17 CFR 210.12-12  12-14]. The
schedules need not be audited.
```

```

```

```

```

```

```

|                 |   |                          | Pioneer Core Equity Fund                                                            |   |                                                                           |
|----------------------|--------|-------------------------------|-------------------------------------------------------------------------------------|--------|--------------------------------------------------------------------------------|
|                 |   |                          | Schedule of Investments 3/31/2017 (unaudited)                                       |   |                                                                           |
|                 |   |                          |                                                                                |   |                                                                           |
| Shares               |   |                          |                                                                                |   | Value                                                                          |
|                 |   |                          | COMMON STOCKS - 98.2%                                                               |   |                                                                           |
|                 |   |                          | Energy - 4.4%                                                                       |   |                                                                           |
|                 |   |                          | Integrated Oil & Gas - 3.7%                                                     |   |                                                                           |
| 704,487              |   |                          | Exxon Mobil Corp.                                                                   | $      | 57,774,979                                                                     |
|                 |   |                          | Oil & Gas Exploration & Production - 0.7%                                   |   |                                                                           |
| 438,616              |   |                          | Cabot Oil & Gas Corp.                                                           | $      | 10,487,309                                                                     |
|                 |   |                          | Total Energy                                                                        | $      | 68,262,288                                                                     |
|                 |   |                          | Materials - 4.9%                                                                    |   |                                                                           |
|                 |   |                          | Fertilizers & Agricultural Chemicals - 1.5%                                     |   |                                                                           |
| 156,718              |   |                          | Agrium, Inc.                                                                        | $      | 14,974,405                                                                     |
| 271,230              |   |                          | CF Industries Holdings, Inc.                                                        |   | 7,960,600                                                                      |
|                 |   |                          |                                                                                | $      | 22,935,005                                                                     |
|                 |   |                          | Specialty Chemicals - 1.2%                                                          |   |                                                                           |
| 62,464               |   |                          | The Sherwin-Williams Co.                                                            | $      | 19,375,708                                                                     |
|                 |   |                          | Paper Packaging - 2.2%                                                              |   |                                                                           |
| 773,598              |   |                          | Sealed Air Corp.                                                                    | $      | 33,713,401                                                                     |
|                 |   |                          | Total Materials                                                                     | $      | 76,024,114                                                                     |
|                 |   |                          | Capital Goods - 6.7%                                                                |   |                                                                           |
|                 |   |                          | Aerospace & Defense - 2.2%                                                      |   |                                                                           |
| 226,120              |   |                          | Raytheon Co.                                                                        | $      | 34,483,300                                                                     |
|                 |   |                          | Building Products - 2.0%                                                            |   |                                                                           |
| 921,549              |   |                          | Masco Corp.                                                                         | $      | 31,323,451                                                                     |
|                 |   |                          | Industrial Machinery - 2.5%                                                         |   |                                                                           |
| 295,809              |   |                          | Illinois Tool Works, Inc.                                                           | $      | 39,185,818                                                                     |
|                 |   |                          | Total Capital Goods                                                                 | $      | 104,992,569                                                                    |
|                 |   |                          | Transportation - 2.9%                                                               |   |                                                                           |
|                 |   |                          | Air Freight & Logistics - 1.9%                                                  |   |                                                                           |
| 272,886              |   |                          | United Parcel Service, Inc. (Class B)                                               | $      | 29,280,668                                                                     |
|                 |   |                          | Trucking - 1.0%                                                                     |   |                                                                           |
| 178,409              |   |                          | JB Hunt Transport Services, Inc.                                                    | $      | 16,367,242                                                                     |
|                 |   |                          | Total Transportation                                                                | $      | 45,647,910                                                                     |
|                 |   |                          | Consumer Durables & Apparel - 1.4%                                              |   |                                                                           |
|                 |   |                          | Footwear - 1.4%                                                                     |   |                                                                           |
| 381,587              |   |                          | NIKE, Inc. (Class B)                                                                | $      | 21,265,844                                                                     |
|                 |   |                          | Total Consumer Durables & Apparel                                               | $      | 21,265,844                                                                     |
|                 |   |                          | Consumer Services - 2.8%                                                            |   |                                                                           |
|                 |   |                          | Restaurants - 2.8%                                                                  |   |                                                                           |
| 754,407              |   |                          | Starbucks Corp.                                                                     | $      | 44,049,825                                                                     |
|                 |   |                          | Total Consumer Services                                                             | $      | 44,049,825                                                                     |
|                 |   |                          | Media - 3.3%                                                                        |   |                                                                           |
|                 |   |                          | Cable & Satellite - 3.3%                                                        |   |                                                                           |
| 1,366,085            |   |                          | Comcast Corp.                                                                       | $      | 51,351,135                                                                     |
|                 |   |                          | Total Media                                                                         | $      | 51,351,135                                                                     |
|                 |   |                          | Retailing - 7.3%                                                                    |   |                                                                           |
|                 |   |                          | Internet Retail - 4.0%                                                              |   |                                                                           |
| 69,844               |   |                          | Amazon.com, Inc. *                                                                  | $      | 61,919,500                                                                     |
|                 |   |                          | Home Improvement Retail - 2.4%                                                      |   |                                                                           |
| 262,583              |   |                          | The Home Depot, Inc.                                                                | $      | 38,555,062                                                                     |
|                 |   |                          | Automotive Retail - 0.9%                                                            |   |                                                                           |
| 93,188               |   |                          | Advance Auto Parts, Inc.                                                            | $      | 13,816,053                                                                     |
|                 |   |                          | Total Retailing                                                                     | $      | 114,290,615                                                                    |
|                 |   |                          | Food & Staples Retailing - 2.8%                                                 |   |                                                                           |
|                 |   |                          | Drug Retail - 2.3%                                                                  |   |                                                                           |
| 460,083              |   |                          | CVS Health Corp.                                                                    | $      | 36,116,516                                                                     |
|                 |   |                          | Food Retail - 0.5%                                                                  |   |                                                                           |
| 262,496              |   |                          | Whole Foods Market, Inc.                                                            | $      | 7,801,381                                                                      |
|                 |   |                          | Total Food & Staples Retailing                                                  | $      | 43,917,897                                                                     |
|                 |   |                          | Food, Beverage & Tobacco - 5.6%                                                 |   |                                                                           |
|                 |   |                          | Brewers - 1.5%                                                                      |   |                                                                           |
| 240,865              |   |                          | Molson Coors Brewing Co. (Class B)                                                  | $      | 23,053,189                                                                     |
|                 |   |                          | Packaged Foods & Meats - 4.1%                                                   |   |                                                                           |
| 234,936              |   |                          | McCormick & Co., Inc.                                                           | $      | 22,918,007                                                                     |
| 369,482              |   |                          | The Hershey Co.                                                                     |   | 40,365,908                                                                     |
|                 |   |                          |                                                                                | $      | 63,283,915                                                                     |
|                 |   |                          | Total Food, Beverage & Tobacco                                                  | $      | 86,337,104                                                                     |
|                 |   |                          | Health Care Equipment & Services - 4.4%                                         |   |                                                                           |
|                 |   |                          | Health Care Supplies - 2.1%                                                         |   |                                                                           |
| 162,588              |   |                          | The Cooper Companies, Inc.                                                          | $      | 32,499,715                                                                     |
|                 |   |                          | Managed Health Care - 2.3%                                                          |   |                                                                           |
| 226,282              |   |                          | Centene Corp. *                                                                     | $      | 16,124,855                                                                     |
| 94,589               |   |                          | Humana, Inc.                                                                        |   | 19,498,576                                                                     |
|                 |   |                          |                                                                                | $      | 35,623,431                                                                     |
|                 |   |                          | Total Health Care Equipment & Services                                          | $      | 68,123,146                                                                     |
|                 |   |                          | Pharmaceuticals, Biotechnology & Life Sciences - 4.5%                           |   |                                                                           |
|                 |   |                          | Biotechnology - 2.5%                                                                |   |                                                                           |
| 159,224              |   |                          | Alder Biopharmaceuticals, Inc.                                                      | $      | 3,311,859                                                                      |
| 197,551              |   |                          | Celgene Corp. *                                                                     |   | 24,581,271                                                                     |
| 101,489              |   |                          | Vertex Pharmaceuticals, Inc. *                                                      |   | 11,097,822                                                                     |
|                 |   |                          |                                                                                | $      | 38,990,952                                                                     |
|                 |   |                          | Pharmaceuticals - 2.0%                                                              |   |                                                                           |
| 911,735              |   |                          | Pfizer, Inc.                                                                        | $      | 31,190,454                                                                     |
|                 |   |                          | Total Pharmaceuticals, Biotechnology & Life Sciences                            | $      | 70,181,406                                                                     |
|                 |   |                          | Banks - 6.5%                                                                        |   |                                                                           |
|                 |   |                          | Diversified Banks - 4.2%                                                            |   |                                                                           |
| 742,587              |   |                          | JPMorgan Chase & Co.                                                            | $      | 65,228,842                                                                     |
|                 |   |                          | Regional Banks - 2.3%                                                               |   |                                                                           |
| 297,385              |   |                          | The PNC Financial Services Group, Inc.                                              | $      | 35,757,572                                                                     |
|                 |   |                          | Total Banks                                                                         | $      | 100,986,414                                                                    |
|                 |   |                          | Diversified Financials - 9.6%                                                       |   |                                                                           |
|                 |   |                          | Specialized Finance - 2.4%                                                          |   |                                                                           |
| 612,226              |   |                          | Intercontinental Exchange, Inc.                                                     | $      | 36,653,971                                                                     |
|                 |   |                          | Consumer Finance - 2.5%                                                             |   |                                                                           |
| 1,113,125            |   |                          | Synchrony Financial                                                                 | $      | 38,180,188                                                                     |
|                 |   |                          | Asset Management & Custody Banks - 2.2%                                         |   |                                                                           |
| 89,612               |   |                          | BlackRock, Inc.                                                                     | $      | 34,367,098                                                                     |
|                 |   |                          | Investment Banking & Brokerage - 2.5%                                           |   |                                                                           |
| 966,254              |   |                          | The Charles Schwab Corp.                                                            | $      | 39,432,826                                                                     |
|                 |   |                          | Total Diversified Financials                                                        | $      | 148,634,083                                                                    |
|                 |   |                          | Insurance - 1.7%                                                                    |   |                                                                           |
|                 |   |                          | Insurance Brokers - 1.7%                                                            |   |                                                                           |
| 358,559              |   |                          | Marsh & McLennan Companies, Inc.                                                | $      | 26,493,925                                                                     |
|                 |   |                          | Total Insurance                                                                     | $      | 26,493,925                                                                     |
|                 |   |                          | Software & Services - 14.1%                                                     |   |                                                                           |
|                 |   |                          | Internet Software & Services - 6.5%                                             |   |                                                                           |
| 53,555               |   |                          | Alphabet, Inc. (Class A)                                                            | $      | 45,403,929                                                                     |
| 35,371               |   |                          | Alphabet, Inc. (Class C)                                                            |   | 29,342,367                                                                     |
| 788,726              |   |                          | eBay, Inc. *                                                                        |   | 26,477,532                                                                     |
|                 |   |                          |                                                                                | $      | 101,223,828                                                                    |
|                 |   |                          | IT Consulting & Other Services - 1.2%                                           |   |                                                                           |
| 315,478              |   |                          | Cognizant Technology Solutions Corp. *                                              | $      | 18,777,251                                                                     |
|                 |   |                          | Data Processing & Outsourced Services - 2.9%                                    |   |                                                                           |
| 497,004              |   |                          | Visa, Inc.                                                                          | $      | 44,168,745                                                                     |
|                 |   |                          | Systems Software - 3.5%                                                             |   |                                                                           |
| 835,405              |   |                          | Microsoft Corp.                                                                     | $      | 55,019,773                                                                     |
|                 |   |                          | Total Software & Services                                                       | $      | 219,189,597                                                                    |
|                 |   |                          | Technology Hardware & Equipment - 7.6%                                          |   |                                                                           |
|                 |   |                          | Communications Equipment - 1.8%                                                     |   |                                                                           |
| 829,613              |   |                          | Cisco Systems, Inc.                                                                 | $      | 28,040,919                                                                     |
|                 |   |                          | Computer Storage & Peripherals - 4.7%                                           |   |                                                                           |
| 510,968              |   |                          | Apple, Inc.                                                                         | $      | 73,405,662                                                                     |
|                 |   |                          | Technology Distributors - 1.1%                                                      |   |                                                                           |
| 295,030              |   |                          | CDW Corp./DE *                                                                      | $      | 17,026,181                                                                     |
|                 |   |                          | Total Technology Hardware & Equipment                                           | $      | 118,472,762                                                                    |
|                 |   |                          | Semiconductors & Semiconductor Equipment - 1.0%                                 |   |                                                                           |
|                 |   |                          | Semiconductors - 1.0%                                                               |   |                                                                           |
| 495,775              |   |                          | Taiwan Semiconductor Manufacturing Co., Ltd. (A.D.R.)                               | $      | 16,281,251                                                                     |
|                 |   |                          | Total Semiconductors & Semiconductor Equipment                                  | $      | 16,281,251                                                                     |
|                 |   |                          | Telecommunication Services - 3.5%                                                   |   |                                                                           |
|                 |   |                          | Integrated Telecommunication Services - 3.5%                                        |   |                                                                           |
| 1,118,413            |   |                          | Verizon Communications, Inc.                                                        | $      | 54,522,634                                                                     |
|                 |   |                          | Total Telecommunication Services                                                    | $      | 54,522,634                                                                     |
|                 |   |                          | Utilities - 3.2%                                                                    |   |                                                                           |
|                 |   |                          | Electric Utilities - 3.2%                                                           |   |                                                                           |
| 734,431              |   |                          | American Electric Power Co., Inc.                                                   | $      | 49,302,353                                                                     |
|                 |   |                          | Total Utilities                                                                     | $      | 49,302,353                                                                     |
|                 |   |                          | TOTAL COMMON STOCKS                                                                 |   |                                                                           |
|                 |   |                          | (Cost $1,323,279,159)                                                               | $      | 1,528,326,872                                                                  |
| Principal Amount ($) |   |                          |
|                 |   |                          | U.S. GOVERNMENT AND AGENCY OBLIGATIONS - 1.3%                                       |   |                                                                           |
| 20,000,000           |   |                          | U.S. Treasury Bills, 4/13/17 (b)                                                    | $      | 19,995,980                                                                     |
|                 |   |                          | TOTAL U.S. GOVERNMENT AND AGENCY OBLIGATIONS                                        |   |                                                                           |
|                 |   |                          | (Cost $19,995,372)                                                                  | $      | 19,995,980                                                                     |
|                 |   |                          |                                                                                |   |                                                                           |
|                 |   |                          | TOTAL INVESTMENT IN SECURITIES - 99.5%                                              |   |                                                                           |
|                 |   |                          | (Cost $1,343,274,530) (a)                                                           | $      | 1,548,322,852                                                                  |
|                 |   |                          | OTHER ASSETS & LIABILITIES - 0.5%                                               | $      | 7,779,828                                                                      |
|                 |   |                          | TOTAL NET ASSETS - 100.0%                                                           | $      | 1,556,102,680                                                                  |
|                 |   |                          |                                                                                |   |                                                                           |
|                 |   |                          |                                                                                |   |                                                                           |
| *                    |   |                          | Non-income producing security.                                                      |   |                                                                           |
|                 |   |                          |                                                                                |   |                                                                           |
| (A.D.R.)             |   | American Depositary Receipts. |                                                                                |   |
|                 |   |                          |                                                                                |   |                                                                           |
| (a)                  |   |                          | At March 31, 2017, the net unrealized appreciation on investments based on          |
|                 |   |                          | cost for federal income tax purposes of $1,345,087,980 was as follows:              |   |                                                                           |
|                 |   |                          |                                                                                |   |                                                                           |
|                 |   |                          | Aggregate gross unrealized appreciation for all investments in which                |   |                                                                           |
|                 |   |                          | there is an excess of value over tax cost                                           | $      |            217,982,028  |
|                 |   |                          |                                                                                |   |                                                                           |
|                 |   |                          | Aggregate gross unrealized depreciation for all investments in which                |   |                                                                           |
|                 |   |                          | there is an excess of tax cost over value                                           |   |            (14,747,156) |
|                 |   |                          |                                                                                |   |                                                                           |
|                 |   |                          | Net unrealized appreciation                                                         | $      |            203,234,872  |
|                 |   |                          |                                                                                |   |                                                                           |
| (b)                  |   |                          | Security issued with a zero coupon. Income is earned through accretion of discount. |

| Various inputs are used in determining the value of the Fund's investments.  These inputs are summarized in the three broad levels listed below. |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                                                                                                                                                       |   |   |   |   |
| Level 1 – quoted prices in active markets for identical securities.                                                                                  |
| Level 2 – other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risk, etc.) |
| Level 3 – significant unobservable inputs (including the Portfolio's own assumptions in determining fair value of investments)                       |
|                                                                                                                                                       |   |   |   |   |
| The following is a summary of the inputs used as of March 31, 2017, in valuing the Fund's investments:                                                     |

|                                                                                       |   | Level 1 |          |   | Level 2 |   |   | Level 3 |   |   | Total  |   |
|--------------------------------------------------------------------------------------------|--------|---------|---------------|--------|---------|--------|--------|---------|--------|--------|--------|--------|
| Common Stocks                                                                              |   | $       | 1,528,326,872 |   |    | $      | -      |    |   | $      | -      |   |   | $ | 1,528,326,872 |   |
| U.S. Government and Agency Obligations                                                     |   |    | 19,995,980    |   |    |   | -      |    |   |   | -      |   |   |   | 19,995,980 |   |
| Total                                                                                      |   | $       | 1,548,322,852 |   |    | $      | -      |    |   | $      | -      |   |   | $ | 1,548,322,852 |   |
|                                                                                       |   |    |          |   |    |   |   |    |   |   |   |   |   |   |   |   |
| During the period ended March 31, 2017, there were no transfers between Levels 1, 2 and 3. |   |    |          |   |    |