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.
Baby rumours reached fever pitch on December 30 with reports that Beyoncé had given welcomed a daughter called Tiana May Carter.
It came after reports suggested that staff at St Luke's Roosevelt Hospital - a private facility in New York - had been told to prepare for a VIP arrival.
But Beyoncé's sister Solange rebutted the rumours by telling fans that the singer had spent New Year's Eve at her house party in Brooklyn.
The 25-year-old confirmed Beyonce was very much still pregnant and tweeted: 'Shout out to my sister for being THE cutest pregnant woman ever!'
Are they parents yet? There has been considerable speculation for weeks after it was falsely reported that the singer and her husband Jay-Z had welcomed their child
The pair dined at the Buttermilk Channel restaurant in Brooklyn, New York.
On Thursday, Beyoncé emerged in public for the first time since being last spotted on December 21.
The 30-year-old was seen stroking her tummy as she was escorted out of a New York office building by a body guard.
The singer was also accompanied by her mother Tina.
Beyoncé announced her pregnancy at the 2011 MTV Video Music Awards back in August.
Showing off the bump: The singer was seen showing off her pregnant shape in New York in NovemberShe arrived on the red carpet cradling her bump.
The singer also showed off her growing tummy after her onstage performance at the same ceremony - unbuttoning her sequined jacket and rubbing her tummy.
Back in October the former Destiny's Child faced internet rumours that she was faking her pregnancy after an interview she did for Australian TV was posted online.
Critics claimed that when the Texan sat down her bump disappeared.
But Beyonce's rep quickly batted down those rumours saying they were 'foolish'.
Big reveal: The singer announced her pregnancy at the MTV VMA's in August
Beyonce's younger sister Solange has a seven-year-old son Daniel Smith JR.
The addition to the Knowles clan will be some welcome good news just weeks after her parents' divorce became final.
Tina and Mathew had been married for 31 years.