Don Costello (September 5, 1901 – October 24, 1945) was an American stage (Broadway) and movie actor. Costello entered films in 1935 and in 1939 was put under contract with MGM. Known for his wicked sense of humor, Costello oftentimes played the role of a menace or a tough guy. He is probably best known for his role as Lefty in the movie Here Comes Mr. Jordan (1941). He appeared in 37 movies (31 times credited), including Another Thin Man (1939), Johnny Eager (1941) and The Blue Dahlia (1946).