Alec Baldwin, Arnold Schwarzenegger, Whoopi Goldberg and other major celebs hit the Big Apple on Tuesday night to celebrate the grand opening of Planet Hollywood.

And, what a party it was … Alec, Arnold and Whoopi were joined in all the fun at the newly reimagined PH venue in Times Square with Alec’s wife, Hilaria, 50 Cent, Pete Davidson, Liev Schreiber, Boy George and Melissa Gorga.

The place was packed to the gills — not just with stars — but also with photogs and ordinary people just out for a good time.

Check it out … Arnold and Alec chat it up with Arnold’s hand resting on Alec’s shoulder as Hilaria stands nearby.

In another clip, Alec, Pete and a third guy sit at a table with Alec talking intensely and throwing a left hook to make his point. Pete just laughs his ass off.

Cut to Alec stuffing his face with tortilla chips while jabbering with Pete. Then Whoopi poses for paparazzi photos with 50 and Arnold in a booth.

And there was much, much more … but you get the picture.