The baby boy, who was born on Wednesday at 3:21 p.m. in Los Angeles, was a week overdue and weighed in at 10 lbs. 9 oz.
"Mother and baby are doing wonderfully," Hargitay's rep, Leslie Sloane, tells PEOPLE. "I just talked to her and she is ecstatic – over the moon."
Hargitay, 42, who plays NYPD detective Olivia Benson on Law & Order: Special Victims Unit, met Hermann, 38, on the NBC show, where he has a recurring role. The couple wed in Santa Barbara, Calif., in August 2004 in front of 200 guests.
Making plans for the baby's arrival, Hargitay told PEOPLE in April, "I want everything ready so that when he comes it'll be all about him." That meant stocking up on "soft, fuzzy things. I want him in swaddles and blankets."
As for staying in shape while she was expecting, Hargitay did prenatal yoga, rubbed Belly Smooches cream on her stomach – and dreamed about two off-limits pursuits: "I'm looking forward to taking a bath and going for sushi!"
Chris Whittle / Jan Knapik / Splash
Hargitay's mother is '50s blonde bombshell Jayne Mansfield, who died in a car crash in 1967. Her father is Hungarian bodybuilder Mickey Hargitay.