Military Sealift Command

The Military Sealift Command (MSC) is a United States Navy organization that controls most of the replenishment and military transport ships of the Navy. It first came into existence on 9 July 1949 when the Military Sea Transportation Service (MSTS) became solely responsible for the Department of Defense's ocean transport needs. The MSTS was renamed the Military Sealift Command in 1970.

Military Sealift Command ships are civilian manned, and are referred to be as being in service, rather than in commission. Some, owned by the United States government, have the prefix USNS, standing for United States Naval Ship, whilst others, on charter or equivalent, are simply the normal merchant MV, SS, or GTS. Their hull numbers have the prefix T- in addition to the normal hull number that an equivalent commissioned ship in the USN would have.

Four programs comprise Military Sealift Command: Sealift, Naval Fleet Auxiliary Force (NFAF), Special Mission, and Prepositioning. The Sealift program provides the bulk of the MSC's supply-carrying operation and operates tankers for fuel transport and dry-cargo ships that transport equipment, vehicles, helicopters, ammunition, and supplies. The NFAF’s role is to directly replenish ships that are underway at sea, enabling them to deploy for long periods of time without having to come to port. The Special Mission program operates vessels for unique military and federal government tasks, such as submarine support and missile flight data collection and tracking. The Prepositioning program sustains the US military's forward presence strategy by deploying supply ships in key areas prior to actual need.