It ain't Babe Ruth, Mickey Mantle or Willie Mays ... no, according to David Ortiz, the greatest baseball player ever is Barry Bonds.
The Red Sox legend made the claim to TMZ Sports out in Beverly Hills this week ... saying Bonds is his MLB G.O.A.T.
"He's the best player of all-time," Big Papi said.
Ortiz added he believes the San Francisco Giants legend is, definitively, a Hall of Famer.
Of course, there's no denying Bonds is statistically the greatest ever ... he hit 762 home runs and stole 514 bases while winning SEVEN MVP awards in his 22 years in the Big Leagues.
The problem ... many believed the former outfielder used performance-enhancing drugs to help his game -- which is why he still hasn't been enshrined in Cooperstown.
Still, it's clear Ortiz believes that's a wrong that needs to righted ... and if you've seen any sorts of Bonds highlights -- it's hard to argue, right?