The baseball Barry Bonds smacked for his last-ever home run is hitting the auction block ... and it could fetch $750,000 (!!!!!!!!!) -- TMZ Sports has learned.
Baseball's home run king launched the final dinger of his career -- No. 762 -- on Sept. 5, 2007 ... when Bonds took Rockies pitcher Ubaldo Jimenez deep at Coors Field in Denver.
It was a mad scramble to catch the ball -- and turns out, for good reason ... 'cause the first time the ball went up for sale back in 2008 -- it sold for $376,612.
Now, we're told the ball is set to hit the auction block on Monday at Goldin Auctions -- and it could fetch three-quarters of a million dollars by the time bidding ends!!!
The ball is a pretty remarkable piece of history ... it has dirt smudges all over it and comes with three separate affidavits that prove its authenticity -- and it could be all yours if ya got the cash.
Bonds -- in addition to being MLB's all-time home run leader -- was a 7-time MVP, 14-time All-Star and 8-time Gold Glove winner.
He finished his 22-year career with a .298 batting average.