Theo Loevendie (born 17 September 1930 in Amsterdam) is a Dutch composer and clarinet player.
Loevendie studied composition and clarinet at the music academy (Conservatorium) of Amsterdam. Initially he concentrated on jazz music. As off 1968 he also wrote concert music, among which operas, concertos and chamber music. Several of his compositions won prizes.
Starting 1970 Loevendie taught composition at several Dutch conservatoires. Among his many students were Svitlana Azarova, Matthias Kadar, Vanessa Lann, Peter van Onna, Robin de Raaff, Victor Varela, Sinta Wullur and Evrim Demirel.
As a performer, he participated in the ensembles Consort, Brevisand the Theo Loevendie Quintet.
In 2004, he founded a new group: The "Ziggurat Ensemble". It consists of a mix of western and non-western instruments: Er-hu, Viola da Gamba, Qanun, Voice, Duduk, Bass, Pan Pipes and Percussion.