The couple announced the birth in a statement today. Faith Margaret Kidman Urban was born to a surrogate Dec. 28 at the Women's Hospital at Centennial Medical Center in Nashville, Tenn.
The baby is the biological child of Urban and Kidman, both 43.
"Our family is truly blessed, and just so thankful, to have been given the gift of baby Faith Margaret," according to their statement. "No words can adequately convey the incredible gratitude that we feel for everyone who was so supportive throughout this process, in particular our gestational carrier."
The two already have a daughter, 2-year-old Sunday Rose.
Kidman found out she was carrying Sunday Rose while she was filming the movie "Australia." She was 40 years old at the time.
In an interview with "Good Morning America" in November 2008, she said doctors had told her she had a 2 percent chance of conceiving a child.
"I was very lucky that ... happened to me because I didn't think that was going to happen in my lifetime. I didn't think I'd get to give birth to ... a child," she said during the interview. "So, yeah, this is my favorite film I've ever made for the rest of my life."
She joked that the magical waters made several women fertile on the set.
"We were swimming in the same water hole and we go, 'See, it was that water hole that got us pregnant.' It's a joke, though. I don't want people going up there and believing that stuff," she said. "I think there was about seven of us that got pregnant and ... took our babies to term. So, yeah, it was a pretty magical film."
Kidman has two adopted children from her previous marriage to Tom Cruise.