James Harden Drops $300K Birthday Gift Bag On Lil Baby with Watch & Honey Buns!

James Harden with the ultimate birthday assist ... because he just hooked up rapper Lil Baby with an insane $300,000 gift bag!!!!

Lil Baby turned 26 this week -- and to celebrate, his good pal, James, turned up with a designer Prada bag loaded with goodies.

"Prada bag 'cause he Prouda' me," Baby said of Harden's gift.

Inside, a bunch of honey bun pastries -- surrounded by a "honey bun," which is slang for $100,000 IN CASH!!!!

(Get it, honey bun -- like a bundle of hundreds?)

There's more ... Baby also pulled out a Richard Mille watch, which appears to come with a $200,000 price tag.

Harden was all smiles as Lil Baby opened up his gifts -- and man, was he stoked!!!

"Don’t Play With Him," Baby posted on IG about Harden ... "How the f*cc I get a bag full of honey buns with a honey bun an a Richard Millie!! Mannn [James Harden] brooooo wtf!! An I’m drunk."

Lil Baby and James Harden have been friends for a while -- most recently vacationing together with some pals on Turks & Caicos.

As for James, he can afford to smother his friends in luxury -- he's reportedly made more than $224 MILLION in his NBA career.