The first USS Merganser (AM-135) was a minesweeper in the United States Navy during World War II.

Originally the commercial trawler Annapolis, Merganser was built in 1937 by the Bethlehem Steel Corp., Quincy, Massachusetts; acquired by the U.S. Navy as Ocean through Maritime Commission requisition purchase from the General Sea Foods Corp., Boston, Massachusetts, 3 January 1942; renamed Merganser 18 January 1942; converted by Bethlehem Steel Atlantic Works, East Boston, Massachusetts; and commissioned 23 May 1942.

Assigned to the 1st Naval District, Merganser operated from the Woods Hole Section Base, patrolling the waters off New England, until February 1944.

She then proceeded to Boston, Massachusetts, for inactivation, decommissioning there 1 May.

She was struck from the Naval Register 16 September, and on the 29th transferred to the Maritime Commission.