The reality star delivered son Mason Dash Disick on Monday morning at Cedars Sinai in Los Angeles, a source confirms to PEOPLE. The baby boy weighed in at 7 lbs., 6 oz., and measured 19.5 inches.
This is the first child for Kardashian, 30, and boyfriend Scott Disick, who announced her pregnancy in August. Kourtney's due date was Dec. 23.
Kardashian, who stars on Keeping Up with the Kardashians and Kourtney & Khloe Take Miami, inititally agonized over whether to continue the pregnancy, and kept the identity of the father private.
The mom-to-be soon found herself embracing pregnancy, sharing that she would be welcoming a son and enjoying her baby shower in November.
"She's changed so much, but I never thought before that Kourtney would have a baby, let alone be the first to have a baby," sister Kim said on Dec. 10. Added Khloe, "The baby is going to put everything in perspective for her."
The birth was first reported by E! News.