The Phantom Planet (1961)
The lead character, astronaut Frank Chapman, played by Dean Fredericks, while traveling though space encounters a race of tiny people on a distant planet. Due to the planet's unusual atmosphere, he is shrunk to six inches in size. Before he finds the remedy to this situation, he is lured by two beautiful women and decides to help the inhabitants of the planet battle an invading race of monsters known as the Solarites.