Beyonce Knowles and Jay-Z have officially confirmed the birth of their daughter with a joint statement released on Knowles' website.
The message read: "Hello Hello Baby Blue!
"We are happy to announce the arrival of our beautiful daughter, Blue Ivy Carter, born on Saturday, January 7, 2012."
Knowles gave birth to the seven pound baby on Sunday night at New York's Lenox Hospital, where the couple reportedly paid nearly $1.7 million to rent out the entire fourth floor.
Jay-Z has also celebrated the birth of his daughter with a rap, titled Glory, paying tribute to Blue.
The proud father describes the birth as "the most amazing feeling i'm feeling" and his "greatest creation".
"You're my child with the child of Destiny's Child. That's a hell of a recipe."
The notoriously private star also alludes to the fact that he and the Halo hitmaker may have suffered a miscarriage in the past, and describes his newborn daughter as "magic".
According to the New York Daily News, the baby's moniker is believed to have a special meaning to the couple, with Jay's seminal 2001 album being titled The Blueprint, while Blue Magic was the first single on his 2007 record American Gangster.
Meanwhile, the Ivy part of her name is said to be a play on the Roman numerals IV, the couple's most-cherished number.
While Beyonce's latest studio album was entitled 4, the pair also got married on April 4.
The singer has previously said: "We all have special numbers in our lives, and four is that for me. It's the day I was born, my mother's birthday, and a lot of my friends' birthdays are on the fourth. April 4 is my wedding date."
Friends and family of the couple have taken to Twitter to congratulate the couple on their new daughter.
Russell Simmons was among the first to celebrate the arrival, tweeting the new parents "congrats to my good friends Beyonce and Jay-Z".
Rihanna also tweeted a welcome to the baby, saying "Welcome to the world princess Carter! Love Aunty Rih."
Knowles' sister, Solange Knowles, tweeted the girl was "the most beautiful girl in the world".
Blue Ivy or Ivy Blue
After initial confusion over the tot's name, with initial reports claiming it was Ivy Ivy Blue, Gwyneth Paltrow confirmed the correct moniker on the micro-blogging site.
The actress - who along with her husband Chris Martin is close friends with Jay-Z and Beyonce - wrote: "Welcome to the world Blue! We love you already. (sic)"
Following an inquiry from a confused user who wrote : "Is it ivy
blue, or blue ivy? so confused", Paltrow replied "It's Blue Ivy
Read the statement or listen to the song here.