Kingston James McGregor Rossdale was born Friday at Cedars-Sinai Medical Center, according to Stefani spokesman Dave Tomberlin. The baby weighed 7 ½ pounds.
"Both mother and child are doing well," Tomberlin said in a statement.
It's the first child for the couple, who were married in 2002. Rossdale, 38, who fronted the rock band Bush, has a 16-year-old daughter with fashion designer Pearl Lowe. He discovered he was the father in 2004 after taking a DNA test.
Stefani, 36, announced her pregnancy in December during a concert in Fort Lauderdale, Fla.
The British-born Rossdale fronted the rock band Bush, which released the popular 1994 album, "Sixteen Stone." They last released the 2001 album, "Golden State," as well as a greatest hits CD in November.