Ben, who starred in hit American show The OC and now stars in Gotham, announced the lovely baby news with his actress wife, Morena, today - but the couple actually welcomed their first child together last week, on 2nd March.
The announcement came via their reps, who also revealed the gender and celebrity baby name they've gone for - a baby girl named Frances Laiz Setta Schenkkan.
'Morena and Ben are so happy to welcome baby girl Frances Laiz Setta Schenkkan on March 2', their reps told USA Today. 'All are happy and healthy and appreciate the well-wishes.'
Just before giving birth and after an intensive press tour for her new film, Deadpool, the actress let everyone know she was being very well treated by her loving partner.
She People magazine: 'I'm finally at the point where I can chill. And Ben is the sweetest. He's giving me extra TLC and making sure I'm drinking water and taking care of myself.'
Ben became famous for his role as Ryan in the O.C.
Ben and Morena are currently playing a couple in the American TV show Gotham, Fox's Batman prequel, and their fictional selves are also expecting a baby together.
Morena, who played Jessica Brody in Homeland, told People the perfect timing of her TV pregnancy was 'a total coincidence'.
'They were already planning on doing that with (our) characters when I got pregnant. When I told them they were like, "Okay, great!" and I was like, "What?" It worked out perfectly', she said.
The two are also a couple in Fox's TV show Gotham
Little Frances is Ben's first child, but Morena is already a mum to two-year-old Julian, whom she had with her now estranged husband, Austin Chick.
The former couple split up last year, and Austin filed for divorce two months before Morena announced her pregnancy.
Ben likes to keep very private about his love life.
'I'm really shy about that stuff. I really don't like relationships to be played out in public. It creates terrible strain. It creates bizarre dynamics' he told Elle. 'There's that saying, "Less said about the bedroom, the better".'
Congratulations to the happy couple!