# EDGAR Filing Document

**Accession Number:** 0001107414
**File Stem:** 0001145549-25-057958
**Filing Date:** 2025-9
**Character Count:** 13356
**Document Hash:** d4916ed636332c8da1a80f1992f80280
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001145549-25-057958.hdr.sgml**: 20250908

**ACCESSION NUMBER**: 0001145549-25-057958

**CONFORMED SUBMISSION TYPE**: N-MFP3

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20250831

**FILED AS OF DATE**: 20250908

**DATE AS OF CHANGE**: 20250908

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** STATE STREET INSTITUTIONAL INVESTMENT TRUST
- **CENTRAL INDEX KEY:** 0001107414

**ORGANIZATION NAME:**
- **EIN:** 046910804
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** N-MFP3
- **SEC ACT:** 1940 Act
- **SEC FILE NUMBER:** 811-09819
- **FILM NUMBER:** 251299070

**BUSINESS ADDRESS:**
- **STREET 1:** ONE IRON STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210
- **BUSINESS PHONE:** 6176643920

**MAIL ADDRESS:**
- **STREET 1:** ONE IRON STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210

## Series and Classes Contracts Data

### State Street Federal Treasury Plus Money Market Fund (Series ID: S000086382)

| Class ID   | Class Name      | Ticker Symbol   |
|:---|:---|:---|
| C000251885 | Advantage Class | ATPXX           |

# Form N-MFP3: Monthly Schedule of Portfolio Holdings

## N-MFP: Filer Information
**Submission Type:** N-MFP3
**CIK:** 0001107414

### General Information

**Report for (YYYY-MM-DD):** 2025-08-31

**Registrant Full Name:** STATE STREET INSTITUTIONAL INVESTMENT TRUST

**CIK Number of Registrant:** 0001107414

**LEI of Registrant:** 549300P1E098W6ES7M39

**Name of Series:** State Street Federal Treasury Plus Money Market Fund

**LEI of Series:** 984500FCIE7E84F01E90

**EDGAR Series Identifier:** S000086382

**Total number of share classes in the series:** 1

**Is this the fund's final filing on Form N-MFP?:** No

**Has the fund acquired or merged with another fund?:** No

## Part A: Series-Level Information about the Fund

### Service Providers
| Role                          | Details                                         | File/CIK Number   |
|:---|:---|:---|
| Investment Adviser            | SSGA Funds Management, Inc.                     | 801-60103         |
| Independent Public Accountant | Ernst & Young  LLP<br>City: Boston<br>State: MA |  |
| Administrator                 | SSGA Funds Management, Inc.                     |  |
| Transfer Agent                | SS&C GIDS, Inc.<br>CIK: 0000027048              | 084-00448         |

### Fund Characteristics & Assets

- **Securities Act File Number:** 333-30810

- **Is this a Feeder Fund?:** Yes

- **Is this a Master Fund?:** No

- **Is this series for insurance company separate accounts?:** No

- **Money Market Fund Category:** Government

- **Is this a Retail Money Market Fund?:** No

- **Is this a Government Money Market Fund?:** No

- **WAM:** 1 days

- **WAL:** 1 days

- **Total Value of Portfolio Securities:** $52335042.80

- **Amortized Cost of Portfolio Securities:** $52335042.80

- **Cash:** $0.00

- **Total Other Assets:** $0.00

- **Total Liabilities:** $195441.78

- **Net Assets of Series:** $52139601.02

- **Number of Shares Outstanding (Series):** 52139586.9500

- **Does the fund seek to maintain a stable price per share?:** Yes

- **Stable Price Per Share:** $1.00

- **Is cash management vehicle an affiliated fund?:** No

- **Does the fund apply liquidity fees?:** No

### Daily & Weekly Liquid Assets
| Date       | Daily Liquid Assets ($)   | Weekly Liquid Assets ($)   | Daily Liquid Assets (%)   | Weekly Liquid Assets (%)   |
|:---|:---|:---|:---|:---|
| 2025-08-01 | $55284365280.78           | $55284365280.78            | 97.2500%                  | 97.2500%                   |
| 2025-08-04 | $57420000051.13           | $57420000051.13            | 97.3600%                  | 97.3600%                   |
| 2025-08-05 | $56269836672.49           | $56269836672.49            | 97.3000%                  | 97.3000%                   |
| 2025-08-06 | $55247627561.27           | $55247627561.27            | 97.2500%                  | 97.2500%                   |
| 2025-08-07 | $53514262335.04           | $53514262335.04            | 97.1700%                  | 97.1700%                   |
| 2025-08-08 | $52632275155.56           | $52632275155.56            | 97.1100%                  | 97.1100%                   |
| 2025-08-11 | $53559135388.46           | $53559135388.46            | 97.1600%                  | 97.1600%                   |
| 2025-08-12 | $54254564126.83           | $54254564126.83            | 97.1900%                  | 97.1900%                   |
| 2025-08-13 | $54682549052.88           | $54682549052.88            | 97.2100%                  | 97.2100%                   |
| 2025-08-14 | $54260671767.36           | $54260671767.36            | 97.1900%                  | 97.1900%                   |
| 2025-08-15 | $55403709411.37           | $55403709411.37            | 97.2500%                  | 97.2500%                   |
| 2025-08-18 | $55642033627.53           | $55642033627.53            | 97.2600%                  | 97.2600%                   |
| 2025-08-19 | $53822474010.00           | $53822474010.00            | 97.1700%                  | 97.1700%                   |
| 2025-08-20 | $53635310998.07           | $53635310998.07            | 97.1600%                  | 97.1600%                   |
| 2025-08-21 | $53251209021.90           | $53251209021.90            | 97.1400%                  | 97.1400%                   |
| 2025-08-22 | $54122669772.22           | $54122669772.22            | 97.1700%                  | 97.1700%                   |
| 2025-08-25 | $54333992597.89           | $54833992597.89            | 97.1900%                  | 98.0800%                   |
| 2025-08-26 | $54572612538.24           | $55072612538.24            | 97.1900%                  | 98.0800%                   |
| 2025-08-27 | $55723199934.13           | $56223199934.13            | 97.2500%                  | 98.1200%                   |
| 2025-08-28 | $57196013468.39           | $57696013468.39            | 97.3100%                  | 98.1600%                   |
| 2025-08-29 | $57212245512.06           | $57332245512.06            | 98.1300%                  | 98.3300%                   |

### 7-Day Gross Yield
| Date       | 7-Day Gross Yield   |
|:---|:---|
| 2025-08-01 | 4.3400%             |
| 2025-08-04 | 4.3400%             |
| 2025-08-05 | 4.3400%             |
| 2025-08-06 | 4.3400%             |
| 2025-08-07 | 4.3400%             |
| 2025-08-08 | 4.3300%             |
| 2025-08-11 | 4.3300%             |
| 2025-08-12 | 4.3300%             |
| 2025-08-13 | 4.3300%             |
| 2025-08-14 | 4.3300%             |
| 2025-08-15 | 4.3300%             |
| 2025-08-18 | 4.3300%             |
| 2025-08-19 | 4.3300%             |
| 2025-08-20 | 4.3300%             |
| 2025-08-21 | 4.3300%             |
| 2025-08-22 | 4.3200%             |
| 2025-08-25 | 4.3200%             |
| 2025-08-26 | 4.3200%             |
| 2025-08-27 | 4.3300%             |
| 2025-08-28 | 4.3300%             |
| 2025-08-29 | 4.3200%             |

### Daily Net Asset Value per Share (Series)
| Date       | Net Asset Value per Share   |
|:---|:---|
| 2025-08-01 | 1.0001                      |
|  |  |
| 2025-08-04 | 1.0001                      |
|  |  |
| 2025-08-05 | 1.0001                      |
|  |  |
| 2025-08-06 | 1.0002                      |
|  |  |
| 2025-08-07 | 1.0001                      |
|  |  |
| 2025-08-08 | 1.0002                      |
|  |  |
| 2025-08-11 | 1.0001                      |
|  |  |
| 2025-08-12 | 1.0002                      |
|  |  |
| 2025-08-13 | 1.0002                      |
|  |  |
| 2025-08-14 | 1.0002                      |
|  |  |
| 2025-08-15 | 1.0002                      |
|  |  |
| 2025-08-18 | 1.0002                      |
|  |  |
| 2025-08-19 | 1.0002                      |
|  |  |
| 2025-08-20 | 1.0001                      |
|  |  |
| 2025-08-21 | 1.0000                      |
|  |  |
| 2025-08-22 | 1.0002                      |
|  |  |
| 2025-08-25 | 1.0001                      |
|  |  |
| 2025-08-26 | 1.0002                      |
|  |  |
| 2025-08-27 | 1.0002                      |
|  |  |
| 2025-08-28 | 1.0002                      |
|  |  |
| 2025-08-29 | 1.0002                      |
|  |  |

## Part B: Class-Level Information about the Fund

### Class: Advantage Class

- **Minimum Initial Investment:** $1000000.00

- **Net Assets of Class:** $52139601.02

- **Number of Shares Outstanding:** 52139586.9500

- **Expense Reimbursement/Waiver:** 4268.18

**Daily Net Asset Value per Share (Class)**
| Date       | NAV per Share   |
|:---|:---|
| 2025-08-01 | 1.0001          |
|  |  |
| 2025-08-04 | 1.0001          |
|  |  |
| 2025-08-05 | 1.0001          |
|  |  |
| 2025-08-06 | 1.0002          |
|  |  |
| 2025-08-07 | 1.0001          |
|  |  |
| 2025-08-08 | 1.0002          |
|  |  |
| 2025-08-11 | 1.0001          |
|  |  |
| 2025-08-12 | 1.0002          |
|  |  |
| 2025-08-13 | 1.0002          |
|  |  |
| 2025-08-14 | 1.0002          |
|  |  |
| 2025-08-15 | 1.0002          |
|  |  |
| 2025-08-18 | 1.0002          |
|  |  |
| 2025-08-19 | 1.0002          |
|  |  |
| 2025-08-20 | 1.0001          |
|  |  |
| 2025-08-21 | 1.0000          |
|  |  |
| 2025-08-22 | 1.0002          |
|  |  |
| 2025-08-25 | 1.0001          |
|  |  |
| 2025-08-26 | 1.0002          |
|  |  |
| 2025-08-27 | 1.0002          |
|  |  |
| 2025-08-28 | 1.0002          |
|  |  |
| 2025-08-29 | 1.0002          |
|  |  |

**Daily Shareholder Flows**
| Date       | Gross Subscriptions ($)   | Gross Redemptions ($)   |
|:---|:---|:---|
| 2025-08-01 | $652815.82                | $133033.16              |
| 2025-08-04 | $762416.20                | $507343.86              |
| 2025-08-05 | $536800.00                | $337938.94              |
| 2025-08-06 | $100400.00                | $333502.04              |
| 2025-08-07 | $388000.00                | $1802794.25             |
| 2025-08-08 | $431000.00                | $165497.89              |
| 2025-08-11 | $283450.00                | $121041.85              |
| 2025-08-12 | $3400.00                  | $50540.66               |
| 2025-08-13 | $1500.00                  | $442469.38              |
| 2025-08-14 | $1247751.15               | $67200.00               |
| 2025-08-15 | $131.19                   | $75000.00               |
| 2025-08-18 | $91636.90                 | $39621.20               |
| 2025-08-19 | $274000.00                | $299860.00              |
| 2025-08-20 | $296960.00                | $517373.03              |
| 2025-08-21 | $806227.73                | $54000.00               |
| 2025-08-22 | $899250.42                | $236608.94              |
| 2025-08-25 | $681995.06                | $381185.59              |
| 2025-08-26 | $500360.00                | $320497.02              |
| 2025-08-27 | $173159.89                | $26000.00               |
| 2025-08-28 | $232551.85                | $99604.46               |
| 2025-08-29 | $79500.00                 | $155000.00              |

**Total Gross Subscriptions (Month):** $8443306.21

**Total Gross Redemptions (Month):** $6166112.27

**7-Day Net Yield (Class)**
| Date       | 7-Day Net Yield   |
|:---|:---|
| 2025-08-01 | 3.9500%           |
| 2025-08-04 | 3.9500%           |
| 2025-08-05 | 3.9500%           |
| 2025-08-06 | 3.9500%           |
| 2025-08-07 | 3.9500%           |
| 2025-08-08 | 3.9400%           |
| 2025-08-11 | 3.9400%           |
| 2025-08-12 | 3.9400%           |
| 2025-08-13 | 3.9400%           |
| 2025-08-14 | 3.9400%           |
| 2025-08-15 | 3.9400%           |
| 2025-08-18 | 3.9400%           |
| 2025-08-19 | 3.9400%           |
| 2025-08-20 | 3.9400%           |
| 2025-08-21 | 3.9400%           |
| 2025-08-22 | 3.9300%           |
| 2025-08-25 | 3.9300%           |
| 2025-08-26 | 3.9400%           |
| 2025-08-27 | 3.9400%           |
| 2025-08-28 | 3.9400%           |
| 2025-08-29 | 3.9300%           |

**Beneficial/Record Owner Categories**
| Category      | Other Category   | Record Owner %   | Beneficial Owner %   |
|:---|:---|:---|:---|
| Broker-dealer |  | 99.8000%         | 0.0000%              |

## Part C: Schedule of Portfolio Securities

### Security 1: State Street Treasury Plus Money Market Portfolio

- **C.1 - Title:** State Street Treasury Plus Money Market Portfolio
- **C.6 - Investment Category:** Investment Company
- **Identifiers:** C.3 - CUSIP: FSSgAK1AW, C.3 - LEI: N/A, C.5 - Other ID: FSSgAK1AW
- **C.18 - Value (incl. sponsor support):** $52335042.80
- **C.18.a - Value (excl. sponsor support):** $52335042.80
- **C.19 - Percentage of Net Assets:** 100.0000%
- **C.17 - Yield as of Reporting Date:** 0.0000%
- **C.11 - Maturity Date (WAM):** 2025-09-02
- **C.12 - Maturity Date (WAL):** 2025-09-02
- **C.13 - Final Legal Maturity Date:** 2025-09-02
- **Characteristics:** C.9 Eligible Security? Yes, C.14 Has Demand Feature? No, C.15 Has Guarantee? No, C.16 Has Enhancement? No, C.22 Is an Illiquid Security? No, C.20 Is a Daily Liquid Asset? Yes, C.21 Is a Weekly Liquid Asset? Yes, C.23 Categorized at Level 3? No

## N-MFP: Signatures

**Registrant:** STATE STREET INSTITUTIONAL INVESTMENT TRUST

**Date:** 2025-09-08

**By:** /s/ Chad Hallett

**Name of Signing Officer:** Chad Hallett

**Title of Signing Officer:** Deputy Treasurer