WHUMPF! ANGIE’s whopping big surprise for partner-in-parenting BRAD PITT.

ANGELINA JOLIE clobbered fiance Brad  with the ultimate 50th birthday gift – a framed autographed poster of boxing great Mike Tyson.

It was a shot right between the eyes for Brad, who had a near-knockout encounter with the former heavyweight champ more than 25 years ago when they were both romantically involved with gorgeous “Head of the Class” actress Robin Givens.

In his autobiography, “Undisputed Truth,” Tyson says he was once waiting to have a tryst with his then-estranged wife Robin when she pulled up in a BMW and Brad stepped out of the passenger seat “looking stoned out of his mind.”

Mike reportedly threatened to put out a hit on Brad’s life! But Tyson swears there are no hard feelings.

And when Angelina, 38, made a personal appeal to him for the signed poster, “he couldn’t have been nicer to her,” said the source.

“He wrote: ‘Yo Brad! Still love your taste in women. Happy 50th Dude. Best Wishes, Mike.’”

As The ENQUIRER has previously reported, the retired fighter, 47, is now pursuing a career in acting.

“Getting a call for a small favor from Angelina Jolie – one of the world’s biggest movie stars – certainly was no imposition to Mike,” the source continued. “He’s well aware of the Hollywood favor bank and knows Angie and Brad both could do wonders to further his career.”

Tyson even called Brad, who hit 50 on Dec. 18, to wish him a happy birthday. As for the poster, it’s hanging in Brad’s gym.

“Brad and Angie are so grateful,” said the source, “they’ve added Mike’s name to their wedding guest list.”