The New York Daily News is reporting that the singer and her husband checked into the Lenox Hill Hospital in Manhattan sometime Friday night.
The couple rented out the entire fourth floor of the hospital for nearly $1.3 million to ensure the highest level of privacy and security.
Several security guards were seen patrolling the area surrounding the hospital, the paper also said.
Twitter was buzzing shortly after.
Singer Rihanna tweeted "Welcome to the world princess Carter! Love Aunty Rih," and music mogul Russell Simmons tweeted "congrats to my good friends Beyonce and Jay-Z."
Representatives for both stars, have yet to comment.
