The music power couple have named their daughter Blue Ivy Carter, according to eonline.com.
The 30-year-old singer gave birth to her daughter by caesarean section at Lenox Hill hospital in New York last night and the website reports 'multiple sources' have confirmed the news.
Russell posted: 'Congrats to my good friends Beyonce and Jay-Z.'
Rihanna posted: 'Welcome to the world princess Carter! Love Aunty Rih.'
Public congratulations: Russell Simmons was one of the first celebrities to tweet the news
Beyoncé, who was spotted out with her mother on Thursday night, is said to have booked out the entire fourth floor spending $1.3million it has been claimed.
While a spokesperson for the power couple was not available for comment security is said to have been tightened at the hospital.
Hospital workers are being asked to turn in their mobile phones and security cameras have been covered, according to the news site.