Star Wars kinda of changed through the script drafts. At some points, it was very deeply indebted to Edgar Rice Burroughs, at other points it was more indebted to Kurosawa, but some of those influences kind of got watered down as the scripts were worked on.

I would say the biggest influences on Star Wars were, by descending order of significance, Flash Gordon, EE Smith's Galactic Patrol, Kurosawa's Hidden Fortress, and Edgar Rice Burroughs A Princess of Mars.

There are other influences like Dune, a whole bunch of World War II movies and, would you imagine, Tolkien's The Hobbit, but they're much more minor.