By TMZ Sports
The jock strap that was used by heavyweight boxing legend Joe Frazier 45 years ago when he beat the greatest of all-time, Muhammad Ali, is about to hit the auction block ... TMZ Sports has learned.
The jock dates back to Ali-Frazier I in 1971 ... known as, "The Fight of the Century," one of America's most historic sporting events. Frazier -- who, like Ali, was undefeated -- won by unanimous decision.
Frazier gave the jock to his buddy the night of the fight ... who held onto it for almost 40 years before selling it to a memorabilia dealer in 2009.
The collector hooked up with Goldin Auctions ... who will now be auctioning off the super rare item starting July 11th. Starting bid is $5K.
FYI -- a Nolan Ryan jock strap worn by the Hall of Famer during his 7th no-hitter reportedly once sold for $25k.
Best part about this jock? It's NEVER BEEN WASHED!! Happy bidding!
