Robert Leffler (9 January 1866 – 15 March 1940) was a German actor, film director and opera singer (bass). Leffler was trained as a singer in Berlin. He began his career in 1889 as a singer and actor at the Basel City Theater, where he stayed until 1891.

Leffler initially appeared primarily as a bass singer at various opera houses such as Nuremberg, Meiningen, Lübeck, Riga, Moscow and Düsseldorf, where he was senior director and opera director at the city theater for 17 years.

From 1919 to 1936 he appeared in 54 films, including the first silent film adaptation of the Buddenbrooks and alongside Hans Albers in several silent films. He also directed 15 films himself.

His older brother Hermann (1864–1929) was also an actor. His brother's wife, his sister-in-law, was the opera singer Martha Leffler-Burkhard (1865–1954).