USS Muskeget (AG-48) – originally USS YAG-9 – was a former commercial cargo ship acquired by the United States Navy in 1941 for use during World War II. She was outfitted with a variety of guns, depth charge tracks, Y-guns, and Mousetrap and placed in service as a patrol vessel. Transferred to the United States Coast Guard for use as a weather ship in the North Atlantic Ocean and renamed USCGC Muskeget (WAG-48), she disappeared in September 1942 with the loss of all on board, the only U.S. weather ship lost during World War II. It was later determined that she had been sunk by a German submarine.