Randy Couture -- Chuck Liddell Gave Me His Shorts ... For Killer Halloween Costume

UFC badass Randy Couture didn't just get Chuck Liddell's approval to become the Iceman for Halloween -- he also got Chuck to give him a pair of his trademark shorts!!!

Couture and his girlfriend Mindy Robinson hit up a huge celebrity costume party in L.A. this weekend -- but before they went inside, Randy gave us the 411 about his outfit.

"Chuck gave me these shorts," Randy told us ... "He gave me these gloves."

If they're fight-used trunks, they could be SUPER VALUABLE ... the shorts Chuck rocked at UFC 66 reportedly fetched more than $8,000 at auction back in 2007.