Welcome to motherhood, Rose Byrne! The actress and her longtime boyfriend Bobby Cannavale welcomed a son together named Rocco, the actor announced during an appearance on "The Late Show with Stephen Colbert."

"I had a baby on Monday, yes," the 45-year-old actor revealed, according to E! News. "You know, I didn't do anything. We [men] don't do anything and I'm so tired. I think I've gained 28 pounds since Monday. I mean, I'm not kidding you. Like, this jacket fit so well, like, last Thursday. But I've been eating so much."

He went on and shared his son's name and said Byrne and the baby are "doing great."

Byrne and Cannavale have been dating since 2012 and have co-starred in numerous films like "Annie," "Adult Beginners" and "Spy," according to The Huffington Post. Rocco is Byrne's first child and Cannavale's second. The actor shares a 20-year-old son with his ex-wife, actress and screenwriter Jenny Lumet.

"It's so much fun," Byrne told People about sharing the screen with Cannavale. "[It] is a very intense thing you can experience together ... It's not for everybody, but I think he's such a great actor."

Congratulations to the couple and their new son.