Manny Pacquiao -- BUYS DIDDY'S OLD MANSION ... And Everything In It!

Manny Pacquiao has just pulled the trigger on Diddy's former Beverly Hills mansion -- TMZ Sports has learned he's officially buying the $12.5 million estate ... AND EVERYTHING INSIDE OF IT!

We broke the story ... Pacman fell in love with the 10,000 square foot pad as soon as he stepped on the property last weekend -- and now our real estate sources say he made the quick decision to buy.

But there was a catch ... Manny wanted to move FAST -- demanding a lightning fast escrow period so his massive Filipino family has a place to stay when they come to L.A. for the fight.

In fact, Manny's in such a rush ... he worked out a deal to get the house fully furnished with the furniture, art and appliances that are currently inside the place.

And get this -- the owners have even agreed to STOCK THE WET BAR for Pacman as part of the deal. Baller stuff.

As we previously reported, Diddy lived in the house in the late '90s (back when he was Puff Daddy) ... and sold it in 2001. The place is sick -- with 7 bedroom, 7.5 baths and a crazy $200,000 home theater.

Perfect for family karaoke nights.