Supplement to the

Fidelity® Corporate Bond Fund

Class A, Class M, Class C, Class I, and Class Z

October 30, 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.

ACBD-ACBDI-SSTK-0424-109-1.924865.109 April 2, 2024

Supplement to the

Fidelity® Intermediate Treasury Bond Index Fund, Fidelity® Long-Term Treasury Bond Index Fund, and Fidelity® Short-Term Treasury Bond Index Fund

April 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.

LBX-I-SSTK-0424-102-1.9899095.102 April 2, 2024

Supplement to the

Fidelity® SAI Long-Term Treasury Bond Index Fund

April 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.

SV5-SSTK-0424-102-1.9899091.102 April 2, 2024

Supplement to the

Fidelity® SAI U.S. Treasury Bond Index Fund

April 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.

UYB-SSTK-0424-102-1.9899092.102 April 2, 2024

Supplement to the

Fidelity® Series Long-Term Treasury Bond Index Fund

April 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.

XS8-SSTK-0424-104-1.9879065.104 April 2, 2024

Supplement to the

Fidelity® SAI Municipal Bond Index Fund

August 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.

MBX-SSTK-0424-103-1.9899437.103 April 2, 2024

Supplement to the

Fidelity® Municipal Bond Index Fund

August 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.

MBL-SSTK-0424-103-1.9899436.103 April 2, 2024

Supplement to the

Fidelity® Corporate Bond Fund

October 30, 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.

CBD-SSTK-0424-106-1.924864.106 April 2, 2024

Supplement to the

Fidelity® Conservative Income Bond Fund

October 30, 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.

FCV-I-SSTK-0424-109-1.927860.109 April 2, 2024

Supplement to the

Fidelity® Series Government Money Market Fund

October 30, 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.

GVM-SSTK-0424-102-1.9883873.102 April 2, 2024

Supplement to the

Fidelity® Series Investment Grade Bond Fund

October 30, 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.

LIG-SSTK-0424-111-1.881203.111 April 2, 2024

Supplement to the

Fidelity® Series Bond Index Fund

October 30, 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.

SBX-SSTK-0424-102-1.9899787.102 April 2, 2024

Supplement to the

Fidelity® Short-Term Bond Index Fund

October 30, 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.

SDX-I-SSTK-0424-102-1.9899405.102 April 2, 2024

Supplement to the

Fidelity® Series Short-Term Credit Fund

October 30, 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.

SS1-SSTK-0424-104-1.9883851.104 April 2, 2024

Supplement to the

Fidelity® U.S. Bond Index Fund

October 30, 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.

UII-UDV-SSTK-0424-112-1.931022.112 April 2, 2024

Supplement to the

Fidelity® Series Corporate Bond Fund

October 30, 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.

XBC-SSTK-0424-103-1.9898001.103 April 2, 2024

Supplement to the

Fidelity Flex® Funds

Fidelity Flex® Conservative Income Bond Fund

October 30, 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.

ZCI-SSTK-0424-103-1.9892886.103 April 2, 2024

Supplement to the

Fidelity Flex® Funds

Fidelity Flex® U.S. Bond Index Fund

October 30, 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.

ZUB-SSTK-0424-102-1.9899403.102 April 2, 2024

Supplement to the

Fidelity® Conservative Income Bond Fund

Class A, Class I, and Class Z

October 30, 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.

AFCV-SSTK-0424-100-1.9912391.100 April 2, 2024

Supplement to the

Fidelity® SAI Municipal Money Market Fund

May 30, 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.

OMM-SSTK-0424-100-1.9912397.100 April 2, 2024