Star-Lord's helmet -- worn by Chris Pratt in "Guardians of the Galaxy" -- was the big winner in a huge movie prop auction this week ... TMZ has learned.

Peter 'Star-Lord' Quill's intergalactic helmet fetched $160,000 in a live auction held Tuesday in the UK by Prop Store ... which was the most of any one item of the 600 on the auction block.

All in all, the auction raked in about $4 million from movie and TV memorabilia.