Zion Williamson Has Post-NBA Draft Pizza Party, Celebrates Til 1 AM!!

PIZZA PARTY!! That's how Zion Williamson -- the hottest pro basketball prospect since LeBron James -- turnt up after getting picked 1st in the NBA Draft!!

After leaving Barclays Center -- mobbed by fans and with an NYPD escort -- Williamson and his fam and friends hit up 800 Degrees Woodfired Kitchen in NYC for a Mardi Gras-themed bash.

(Yeah, good thing the New Orleans Pelicans picked Zion ... 'cause if they didn't, that would've been a very awkward party.)

We're told the restaurant -- which was shut down to the public -- served up a bunch of pizzas, burgers, salads and seafood for the superstar baller and his crew. They also had a pop-a-shot in the house.

Zion wasn't the only hooper in attendance ... Cleveland Cavaliers point guard Collin Sexton -- the 8th pick in last years draft -- stopped by to congratulate his buddy.

The bash was the cap to an emotional night for Williamson ... who broke down and started crying while thanking his mom after getting picked.

The party didn't stop til around 1 AM ... when Zion finally called it a night.

FYI -- 800 Degrees is pretty popular with the NBA crowd ... Dwyane Wade and Udonis Haslem own the Miami location.