Inmarsat-3 F4 is a communications satellite operated by the British satellite operator Inmarsat. It was launched into a geosynchronous orbit on 4 June 1997. It was located at 54° West longitude whilst in service, providing coverage of the Americas as AOR-W. It was replaced by Inmarsat-3 F5 at 54° West in Feb 2016, and the now-retired Inmarsat-3 F4 was moved to parking at 144° West.

Inmarsat-3 F4 was constructed by Lockheed-Martin, using an AS-4000 bus. It has a mass of 2,068 kilograms and is expected to operate for 13 years.

In the United States, Inmarsat ground stations are licensed to operate at 1525-1559 MHz and 1626.5-1660.5 MHz via a mechanism called the ISAT List. The 1544-1545 MHz and 1645.5-1646.5 MHz bands are reserved for safety and distress communications.

INSAT-2D, identical to INSAT-2C, was launched on June 4, 1997, but the satellite became in-operable since October 4, 1997, following a power bus anomaly and associated problems. Hence it was replaced by the in-orbit satellite ARABSAT-1C, designated as INSAT-2DT.