|        |
|--------|
|        |  |
| ý | QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|        |
|--------|
|        |  |
|  ̈ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|                                                               |
|---------------------------------------------------------------|
|                                                               |  |  |
| Washington                                                    |   | 91-1223280 |
| (State or other jurisdiction ofincorporation or organization) |   | (I.R.S. Employer                    Identification No.) |

|                                                                  |
|------------------------------------------------------------------|
|                                                                  |  |  |
| Large accelerated filer ý                                   |    | Accelerated filer o |
| Non-accelerated filer o (Do not check if a smaller company) |    | Smaller reporting company o |

----

----

|               |
|---------------|
|               |  |  |  |  |  |  |  |  |  |  |
|          |   |   |   |   |   | Incorporated by Reference |
| ExhibitNumber |   | Exhibit Description |   | FiledHerewith |   | Form |   | Period Ending |   | Filing Date |
|          |   |   |   |   |   |   |   |   |   |   |
| 3.1           |   | Articles of Incorporation as amended of the registrant |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 3.2           |   | Bylaws of the registrant |   |   |   | 8-K |   |   |   | 8/24/2010 |
|          |   |   |   |   |   |   |   |   |   |   |
| 4.1           |   | Form of 1.750% Senior Notes due February 15, 2020 |   |   |   | 8-K |   |   |   | 2/5/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 4.2           |   | Form of 2.250% Senior Notes due February 15, 2022 |   |   |   | 8-K |   |   |   | 2/5/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 10.1          |   | Citibank, N.A. Co-Branded Credit Card Agreement* |   | x |   |   |   |   |   |   |
|          |   |   |   |   |   |   |   |   |   |   |
| 31.1          |   | Rule 13(a) - 14(a) Certifications |   | x |   |   |   |   |   |   |
|          |   |   |   |   |   |   |   |   |   |   |
| 32.1          |   | Section 1350 Certifications |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.INS       |   | XBRL Instance Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.SCH       |   | XBRL Taxonomy Extension Schema Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.CAL       |   | XBRL Taxonomy Extension Calculation Linkbase Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.DEF       |   | XBRL Taxonomy Extension Definition Linkbase Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.LAB       |   | XBRL Taxonomy Extension Label Linkbase Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |
|          |   |   |   |   |   |   |   |   |   |   |
| 101.PRE       |   | XBRL Taxonomy Extension Presentation Linkbase Document |   |   |   | 10-Q |   | 5/10/2015 |   | 6/4/2015 |

----

|                 |
|-----------------|
|                 |  |  |  |
|            | COSTCO WHOLESALE CORPORATION(Registrant) |
|            |   |   |
| August 31, 2015 | By |   | /s/ W. CRAIG JELINEK |
| Date            |   |   | W. Craig JelinekPresident, Chief Executive Officer and Director |