Eje Thelin (born Eilert Ove Thelin) (June 9, 1938 – May 18, 1990) was an innovative Swedish trombonist, widely admired among fellow trombonists for his facile technique and rhythmic intensity. He was, perhaps, the first jazz trombonist to translate that technique into the so-called "sheets of sound" style that characterized much of the music of tenor saxophonist John Coltrane and, in general, Free Jazz of the late 1960s and 1970s.
Thelin started his own quintet in 1961. From 1968 to 1972 he was on the faculty of the Music Academy in Graz, Austria. For the rest of the 1970s, he led his own Eje Thelin Group in Sweden. In the 1980s he expanded into composition, writing commissioned works for large European orchestras, sometimes featuring himself as soloist. In spite of the attention given to the obvious technical side of his playing, Thelin was also known for his warm approach to traditional ballads, a somewhat retro-romanticism that comes through in his later playing.