The rapper rented out Ysabel in West Hollywood Sunday night for his 32nd birthday, and among the dinner guests were Future, Rick Ross, Ty Dolla $ign, Lil Yachty, Young Thug, YG, DJ Mustard, Yo Gotti and Diddy's son, Justin.

The fellas really appeared to enjoy each other's company ... along with some cake and drinks, including a customized "Dream Chaser" cocktail by D'Usse VSOP in Meek's honor.

YG also rocked a vest in tribute of their late pal, Nipsey Hussle.

We're told Meek gathered everyone together and delivered a speech thanking them for their support during his ups and downs ... and toasted to his #1 album, "Championships," and the launch of the REFORM Alliance, which is dedicated to prison reform.

As you know ... Meek was released from prison on bail a little more than a year ago, and has been working hard as an advocate for criminal justice reform ever since.