Little Bronx weighed in at 7 pounds, 11 ounces, according to a statement from the couple's publicist.
"Ashlee, Pete and baby Bronx are all healthy and happy," the statement read, "and thank everyone for their well wishes!"
He's the first child for both ... and his birth was, shall we say, rather anticipated.
Several reports had Simpson going into labor last weekend, and though that information proved to be incorrect, Simpson was so close to delivering that Wentz opted to stay with her in Los Angeles rather than attend Sunday night's "Total Finale Live" in New York with his Fall Out Boy mates, though he did call in during the show.
Simpson and Wentz were engaged in April and married the following month. Almost immediately, rumors began to circulate that Simpson was pregnant, though in an e-mail to MTV News, Wentz dismissed those rumors as "a witch hunt." He later joked in a radio interview with Ryan Seacrest that "this baby is not confirmed."
Of course, that all changed within a few days, when the couple announced in a post on FriendsOrEnemies.com that they were, in fact, expecting a child. Wentz then wrote another e-mail to MTV News, explaining that he had denied Simpson was pregnant because "we wanted to wait until after the first trimester and get a clean bill of health from our doctors. ... Being a boy, I have no idea how to respond to such things, and my first instinct was to protect [Ashlee] and the baby."