The child is the first for Kardashian and Scott Disick, her boyfriend of two years.
"Kourtney just delivered a healthy baby boy about an hour ago," her representative told E! News and Life & Style magazine Monday morning.
"A boy is definitely needed in this family!" Kardashian told E! News in October. "Scott and I are thrilled to add a little boy to the bunch."
"We're home every night looking at baby books and baby magazines," Disick told Usmagazine.com before the baby's birth. "I just want to stay home with (Kourtney,) enjoy her company, look at her stomach and be with her."
Kardashian is known for her TV programs "Keeping Up with the Kardashians" and "Kourtney and Khloe Take Miami."