Jennings and de Matteo
Rick Maiman/AP
The actress, 35, and musician boyfriend Shooter Jennings, 28, welcomed their daughter on Wednesday night, a rep for the actress tells E! Online's Marc Malkin.
"Family and baby are happy and healthy," the actress's rep, Amanda Slverman, said in a statement.
Alabama is the first child for the couple, who have been dating for six years.
De Matteo, who played Adriana La Cerva on the HBO drama and also starred in the NBC sitcom Joey, announced the pregnancy in May.
In June, even before she knew the gender, De Matteo had a feeling she was having a girl. "I use 'she,' because I'm getting so fat, I think it's a girl!" she said at the time.
Jennings is the son of the late country legend Waylon Jennings.
