Although the U.S. version of the film was advertised under the title "King of Kong Island", its actual on-screen title is "Kong Island," even though the film has nothing to do with King Kong.
Riffed in 2024 by the MST3K team under the Rifftrax name.
Fred Olan Ray stated in his DVD's Elvira-like introduction that not only is King Kong not on the island, but the movie itself doesn't take place on an island.
Golden Age actor Marc Lawrence had been blacklisted in the 1950's (after attempting to blame his accusations on fellow tough guy actor Lionel Stander, also blacklisted), so he worked primarily in Italian movies. By this time the blacklist was well over, and he worked in American films and television. But starring in a low-budget Italian movie was nothing new to him.
Kong Island got the title after the movie was made, to trick audiences into thinking it's connected to King Kong. The original title is Eva, la Venere selvaggia, which translates from Italian to English as, EVA: THE WILD VENUS, which is the true title of the film.