The Schweizer SGS 1-21 is a United States single-seat, mid-wing, Open Class glider built by Schweizer Aircraft of Elmira, New York. The 1-21 was a clean-sheet design intended to fill the role of high performance competition sailplane. It was designed by Ernest Schweizer and first announced in the September–October 1946 issue of the Soaring Society of America's Soaring magazine.