Angels star Anthony Rendon -- a former World Series champion -- was involved in a heated confrontation with an A's supporter following L.A.'s loss on Thursday ... one where he grabbed the fan and then attempted to take a swipe at the guy's face.

The altercation happened just seconds after the Halos lost at RingCentral Coliseum in Oakland, 2-1 -- when Rendon believed a fan had called him "a bitch" near their dugout.

The L.A. third baseman was so upset over it, he locked his hand around the guy's tee, and pulled him down to the railing.

Video shows Rendon said to the man, while still grabbing his shirt, "You called me a bitch, huh?"

When the guy responded that he did not, the baseball player added, "Yeah, you did. Yeah, you did. Yeah, motherf*****."

Rendon then let go of the man, but made a clear attempt to hit the guy in the face after he released the shirt.

Fortunately, the man pulled away before Rendon could make contact.

The 32-year-old MLB star then said, "Get your bitch-ass out of here" -- before he headed into the locker room without further incident.

It's not known if the Angels are aware of the tiff -- the team told us on Friday morning it had no comment.

The Oakland Police Dept., meanwhile, said Friday it is not investigating the matter ... explaining in a statement, "No victim(s) reached out to the Oakland Police Department regarding this incident."

It's been a frustrating few seasons for Rendon since he left the Washington Nationals in 2019 and inked a seven-year, $245 million contract with L.A. ... as he's battled multiple injuries, which have limited him to just 158 games over the past four years.