The actor hit the stage at the David H. Koch theater with the film's cast and director Shawn Levy -- and while delivering his speech, Ryan revealed the name of his youngest kid: Olin.

He then thanked his wife, Blake Lively, who was sitting in the crowd, while giving her props for her stunning tight red ensemble, calling it amazing.

After that, Ryan praised their 4 children: James, Inez, Betty and Olin, saying he loves his whole family.

This was the first time the name of the couple's fourth child had been mentioned publicly since Olin was born on February 12, 2023. But, the pair has kept Olin's gender a secret.

You may recall in May ... Ryan joked with "Today" show host Savannah Guthrie that he and Blake always wait for their close friend Taylor Swift to tell them the names of their youngsters.

Meanwhile, other major celebs also showed up at the "Deadpool & Wolverine" premiere last night, including Hugh Jackman, Gigi Hadid, Avril Lavigne, Matt Rife and Jimmy Fallon. Of course, Jackman plays Wolverine opposite Reynolds' character Deadpool in the flick.