Sergej Mašera (May 11, 1912 – April 17, 1941) was a naval Lieutenant of the Yugoslav Royal Navy.
At the end of the April War, Mašera, along with his fellow Lieutenant Milan Spasic, scuttled the destroyer Zagreb in the Bay of Kotor near Tivat to prevent its capture by the Italian Royal Navy (Regia Marina Italiana).
Both lieutenants died in the explosion, and were posthumously made members of the Order of the People's Hero.