Megan Thee Stallion No, We're Not Engaged ... Just Celebratin' Our Anniversary!!!

Chill. That's not the full story ... according to folks in her camp, and Megan herself.

Sources connected to Megan tell TMZ ... Meg and her BF Pardi celebrated their 2nd anniversary Tuesday night at Brooklyn Chop House Times Square -- we're told Pardi picked the place because he's really tight with the owner, Don Pooh, and it's a go-to for the rapper.

They were in New York following Meg's SNL performance, and decided to stay in town to celebrate their milestone.

As for the event, we're told Pardi set the whole thing up himself as a surprise -- spending hours on the phone with the venue to make sure everything was just right.

She was given a great night ... dining privately on the roof, which was decorated with a bunch of candles and over 1,000 balloons. She was given a HUGE bunch of roses when she walked in, too.

Meg was seen leaving the dinner with a bunch of diamonds on her left ring finger -- y'know ... the engagement one. We're told it's actually FIVE diamond rings, but the bummer part for fans is that they were a gift ... from her stylist ... not Pardi.

Meg even responded to the rumors ... saying, "Lol as nice as last night was we are not engaged."