Otakar Mařák (5 January 1872 Esztergom, Hungary – 2 July 1939 Prague) was a Czech opera singer (a tenor), and a nephew of Julius Mařák, who perfected his vocal skills at Prague's School of Applied Arts as well as at the Czech Academy of Arts.

Mařák made his debut in the title role of Charles Gounod's opera Faust on 1 February 1899 in Brno, Czech Republic.

[clarification needed] In 1907 he left for Paris, where he continued to school his voice then in 1908–1918 performed at London's Covent Garden and Berlin's Komische Oper.

He especially excelled in Smetana parts such as Jeník in The Bartered Bride, Dalibor, Ladislav Podhajský in The Two Widows, Lucas in The Kiss as well as in traditional world repertory which saw Mařák play Don Ottavio in Don Giovanni, Massenet's Werther, Cavaradossi in Tosca and Alfred Germont in La Traviata.

Together with Emmy Destinn and Karel Burian, Mařák completed the trio of well-known early 20th century Czech singers.