Gösta Theselius (June 9, 1922 in Stockholm – January 24, 1976 in Stockholm) was a Swedish arranger, composer, film scorer, pianist, and saxophonist. His brother was musician Hans Theselius.
Theselius worked in the 1940s with a number of European big bands, including those of Thore Jederby, Hakan von Eichwald, Sam Samson, Lulle Elboj, and Thore Ehrling. He played jazz into the 1950s, both as a saxophonist and a pianist (on the latter instrument with Benny Bailey, Arne Domnerus, James Moody, and Charlie Parker), and composed copiously for film in the 1950s and 1960s.