The comedian said she gave birth at 10:55 p.m. Sunday in an Instagram post showing her and Fischer holding the baby in a hospital room.
Schumer also referenced the royal baby when she announced her pregnancy in October, photoshopping an image of her and Fischer's faces on the bodies of the duke and duchess of Sussex.
Schumer had a difficult pregnancy with a severe case of hyperemesis, or morning sickness. In February, doctors advised her not to fly and she canceled the remaining dates on her standup comedy tour.
Schumer and Fischer married in February 2018. They did not announce their child's name.