USS SC-521 was a SC-497 class submarine chaser that served in the United States Navy during World War II. She was laid down on 5 May 1941 by the Annapolis Yacht Yard, Inc. in Annapolis, Maryland and launched on 1 February 1942. She was commissioned on 15 April 1942. She foundered on 10 July 1945 off Santa Cruz, Solomon Islands.