# EDGAR Filing Document

**Accession Number:** 0001107414
**File Stem:** 0001193125-26-076122
**Filing Date:** 2026-2
**Character Count:** 7243
**Document Hash:** 067c36e26f52706c3806dfad7953d8b6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-076122.hdr.sgml**: 20260226

**ACCESSION NUMBER**: 0001193125-26-076122

**CONFORMED SUBMISSION TYPE**: 485BXT

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260226

**DATE AS OF CHANGE**: 20260226

**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:** 485BXT
- **SEC ACT:** 1940 Act
- **SEC FILE NUMBER:** 811-09819
- **FILM NUMBER:** 26686854

**BUSINESS ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114
- **BUSINESS PHONE:** 6176643920

**MAIL ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114
**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:** 485BXT
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-30810
- **FILM NUMBER:** 26686853

**BUSINESS ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114
- **BUSINESS PHONE:** 6176643920

**MAIL ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114

## Series and Classes Contracts Data

### State Street Federal Prime Retail Reserves Money Market Fund (Series ID: S000101207)

| Class ID   | Class Name            | Ticker Symbol   |
|:---|:---|:---|
| C000271297 | Advisory Class        |  |
| C000271298 | Advantage Class       |  |
| C000271299 | Cash Management Class |  |
| C000271300 | Capital Class         |  |
| C000271301 | Agency Class          |  |

**As filed with the Securities and Exchange Commission on February 26, 2026** 

**Securities Act File No. 333-30810** 

**Investment Company Act of 1940 File No. 811-09819** 

**UNITED STATES** 

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

**FORM N-1A** 

**REGISTRATION STATEMENT** 

***UNDER***

---

| | |
|:---|:---|
| ***THE SECURITIES ACT OF 1933*** | ☒ |
| **Post-Effective Amendment No. 322** | ☒ |

---

**And** 

**REGISTRATION STATEMENT** 

***UNDER***

---

| | |
|:---|:---|
| ***THE INVESTMENT COMPANY ACT OF 1940*** | ☒ |
| **Amendment No. 324** | ☒ |

---

## STATE STREET INSTITUTIONAL INVESTMENT TRUST
**(Exact Name of Registrant as Specified in Charter)** 

**One Congress Street** 

**Boston, Massachusetts 02114** 

**(Address of Principal Executive Offices)** 

**Registrant's Telephone Number: (617) 664-3920** 

**Andrew J. DeLorme, Esq.** 

**Chief Legal Officer** 

**c/o SSGA Funds Management, Inc.** 

**One Congress Street** 

**Boston, Massachusetts 02114** 

**(Name and Address of Agent for Service)** 

***Copies to:***

**Adam M. Schlichtmann, Esq.** 

**Ropes & Gray LLP** 

**Prudential Tower, 800 Boylston Street** 

**Boston, Massachusetts 02199-3600** 

It is proposed that this filing will become effective:

☐ immediately upon filing pursuant to Rule 485, paragraph (b)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;☒ on March 6, 2026 pursuant to Rule 485, paragraph (b)

☐ 60 days after filing pursuant to Rule 485, paragraph (a)(1)

☐ on _________________ pursuant to Rule 485, paragraph (a)(1)

☐ 75 days after filing pursuant to Rule 485, paragraph (a)(2)

☐ on _________________ pursuant to Rule 485, paragraph (a)(2)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;☒ this post-effective amendment designates a new effective date for a previously filed post-effective amendment.

------

NOTE: This Post-Effective Amendment No. 322 to the Registrant's Registration Statement on Form N-1A is being filed pursuant to paragraph (b)(1)(iii) of Rule 485 under the Securities Act of 1933, as amended (the "Securities Act"), solely for the purpose of delaying, until March 6, 2026, the effectiveness of [Post-Effective Amendment No. 315](http://www.sec.gov/Archives/edgar/data/1107414/000119312525290916/d74499d485apos.htm)to the Registrant's Registration Statement on Form N-1A, with respect to the State Street<sup>®</sup> Federal Prime Retail Reserves Money Market Fund, which was filed pursuant to Rule 485(a) under the Securities Act on November 21, 2025 (the "Amendment").

Part A. INFORMATION REQUIRED IN A PROSPECTUS

[Part A is incorporated by reference to Part A of the Amendment.](http://www.sec.gov/Archives/edgar/data/1107414/000119312525290916/d74499d485apos.htm)

Part B. INFORMATION REQUIRED IN A STATEMENT OF ADDITIONAL INFORMATION

[Part B is incorporated by reference to Part B of the Amendment.](http://www.sec.gov/Archives/edgar/data/1107414/000119312525290916/d74499d485apos.htm)

Part C. OTHER INFORMATION

[Part C is incorporated by reference to Part C of the Amendment.](http://www.sec.gov/Archives/edgar/data/1107414/000119312525290916/d74499d485apos.htm)

------

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant, State Street Institutional Investment Trust (the "Trust"), certifies that it meets all the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b)(1)(iii) under the Securities Act of 1933, as amended, and has duly caused this Amendment to the Registration Statement to be signed on its behalf by the undersigned, thereunder duly authorized, in the City of Boston and the Commonwealth of Massachusetts on the 26<sup>th</sup> day of February, 2026.

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| | |
|:---|:---|
| STATE STREET INSTITUTIONAL INVESTMENT TRUST | STATE STREET INSTITUTIONAL INVESTMENT TRUST |
| By: | /s/ Ann M. Carpenter |
|  | Ann M. Carpenter |
|  | President |

---

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated:

---

| | | |
|:---|:---|:---|
| **SIGNATURES** | **TITLE** | **DATE** |
| /s/ Patrick J. Riley\* | Trustee | February 26, 2026 |
| Patrick J. Riley |  |  |
| /s/ Donna M. Rapaccioli\* | Trustee | February 26, 2026 |
| Donna M. Rapaccioli |  |  |
| /s/ Margaret K. McLaughlin\* | Trustee | February 26, 2026 |
| Margaret K. McLaughlin |  |  |
| /s/ George M. Pereira\* | Trustee | February 26, 2026 |
| George M. Pereira |  |  |
| /s/ Mark E. Swanson\* | Trustee | February 26, 2026 |
| Mark E. Swanson |  |  |
| /s/ Jeanne LaPorta\* | Trustee | February 26, 2026 |
| Jeanne LaPorta |  |  |
| /s/ Ann M. Carpenter<br> Ann M. Carpenter | President (Principal Executive Officer) | February 26, 2026 |
| /s/ Bruce S. Rosenberg<br> Bruce S. Rosenberg | Principal Accounting Officer and Principal Financial Officer | February 26, 2026 |

---

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| | |
|:---|:---|
| \*By: | /s/ E. Gerard Maiorana, Jr. |
|  | E. Gerard Maiorana, Jr. |
|  | As Attorney-in-Fact<br> Pursuant to Power of Attorney |

---

\* Signature affixed by Edmund Gerard Maiorana, Jr. pursuant to a power of attorney dated January 21, 2025