Supplement to the

Fidelity® Government Money Market Fund

Capital Reserves Class and Daily Money Class

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

P13-CR-DM-SSTK-0424-101-1.9869889.101 April 2, 2024

Supplement to the

Fidelity® Government Money Market Fund, Fidelity® Money Market Fund, and Fidelity® Treasury Only Money Market Fund

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, each fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contracts" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

SMF-SSTK-0424-126-1.713588.126 April 2, 2024

Supplement to the

Fidelity® Series Treasury Bill Index Fund

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

XSB-SSTK-0424-101-1.9901254.101 April 2, 2024

Supplement to the

Fidelity® Government Money Market Fund and Fidelity® Money Market Fund

Premium Class

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, each fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contracts" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

P13-P14-SSTK-0424-100-1.9912398.100 April 2, 2024

Supplement to the

Fidelity® Government Money Market Fund

Class K6

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

SPU-K6-SSTK-0424-100-1.9912400.100 April 2, 2024

Supplement to the

Fidelity® Government Money Market Fund

Class M

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

SPU-M-SSTK-0424-100-1.9912401.100 April 2, 2024

Supplement to the

Fidelity® Government Money Market Fund

Class S

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

SSPU-SSTK-0424-100-1.9912403.100 April 2, 2024

Supplement to the

Fidelity Flex® Funds

Fidelity Flex® Government Money Market Fund

June 29, 2023

STATEMENT OF ADDITIONAL INFORMATION

Effective March 1, 2024, the fund's sub-advisory agreements with FMR Investment Management (UK) Limited, Fidelity Management & Research (Hong Kong) Limited, and Fidelity Management & Research (Japan) Limited were amended. The following information supplements similar information found in the "Management Contract" section.

Under the terms of the sub-advisory agreements, FMR pays each sub-adviser monthly fees equal to 110% of the sub-adviser's costs for providing sub-advisory services.

ZGY-SSTK-0424-100-1.9912405.100 April 2, 2024