Cyrillus Kreek (born as Karl Ustav Kreek; 3 December [O.S. 21 November] 1889 in Võnnu, Lääne county – 26 March 1962 in Haapsalu) was an Estonian composer. Kreek studied trombone and composition at the Saint Petersburg Conservatory from 1908 to 1916 in the years immediately prior to the Russian Revolution, then worked as music teacher first in his native Haapsalu (in western Estonia), at the Tartu Music College and later at the Tallinn Conservatory.