Bride of the Gorilla (1951)

Raymond Burr (of Perry Mason fame) stars as Barney Chavez, a plantation manager working deep in the South American jungle. Barney has a yen for the beautiful wife of his employer, and decides to murder the old man to have her for himself. Unfortunately for Barney a native sorcerer witnesses the crime, and puts a curse on him that transforms him by night into a murderous gorilla.