Doctor Septimus Pretorius is a fictional character who appears in the Universal film Bride of Frankenstein (1935) as the main antagonist. He is played by British stage and film actor Ernest Thesiger. Some sources claim he was originally to have been played by Bela Lugosi or Claude Rains. Others indicate that the part was conceived specifically for Thesiger.

Bride of Frankenstein is a 1935 American science fiction horror film, and the first sequel to Universal Pictures' 1931 film Frankenstein. As with the first film, Bride of Frankenstein was directed by James Whale starring Boris Karloff as the Monster and Colin Clive as Dr. Frankenstein. The sequel features Elsa Lanchester in the dual role of Mary Shelley and the bride. Colin Clive reprises his role as Henry Frankenstein, and Ernest Thesiger plays the role of Doctor Septimus Pretorius. Oliver Peters Heggie plays the role of the old blind hermit.