It was surf god meets Norse god in Australia ... when "Thor" star Chris Hemsworth hit the beach with Kelly Slater for a celeb surf session ... while Chris' famous bro Liam played the role of photog.
Chris and Kelly paddled out together yesterday in Byron Bay -- where they caught waves, shot the breeze and escaped the clutches of the great white sharks that frequent the area.
The entire surf sesh was caught on video by Chris' lil bro Liam Hemsworth -- who's not exactly small potatoes .