Stephen C. Apostolof (25 February 1928 in Burgas, Bulgaria - 14 August 2005, Mesa, Arizona), sometimes credited under aliases A.C. Stephen(s) or Robert Lee, was a Bulgarian-American filmmaker specializing in the "erotic" film genre.

Born in the Bulgarian Black Sea town of Burgas, he claimed asylum in the US in the 1940s. His large body of work was produced mainly between the late 1960s and the late 1970s. In 1957 he produced Journey to Freedom (1957), an anti-Communist picture inspired by his own life. The film teamed Apostolof with director of photography William C. Thompson and Swedish-born actor 'Tor Johnson', both now best-known for their work with the infamous director Edward D. Wood Jr.. Thompson later introduced Apostolof to Wood. In an interview conducted in the beginning of the 1990s, Apostolof recalls his first meeting with the eccentric director, who appeared at the "Brown Derby" restaurant in Los Angeles, in drag and with a mustache.

Apostolof made his directorial debut with Orgy of the Dead (1965). Ed Wood wrote the script and acted as production assistant. The film starred Criswell, the famous television oracle immortalized in Wood's Plan 9 from Outer Space (1957). Outtakes from this film and interview segments with Apostolof are included in the 1994 documentary Ed Wood: Look Back in Angora (1994), released by Rhino Home Video. During the 1960s and 1970s Apostolof directed nine screenplays written by Wood.

Apostolof was interviewed for an in-depth article on the making of "Orgy of the Dead" in the horror/science fiction magazine Femme Fatales (7:1, June 1998). In 1990 the specialized magazine Psychotronic Video published an eight-page interview with Apostolof entitled "Stephen C. Apostoloff: Bulgarian nude director".

Stephen Apostolof died on August 14, 2005, aged 77. He is survived by his second wife and five children.