And, as is now tradition, his parents Prince William and Kate Middleton have released beautiful new photos of their eldest child, taken by photographer Matt Porteous at Anmer Hall in Norfolk, to mark the occasion.
He is one serious cutie, right?
Happy 3rd Birthday Prince George . . Prince George of Cambridge was born weighing 8 pounds 6 ounces (3.80 kg) at 16:24 on 22 July 2013. . This marked the second time that three generations of direct heirs to the British throne have been alive at the same time, a situation that last occurred between 1894 and 1901, in the last seven years of the reign of Queen Victoria. . The birth took place in the Lindo Wing of St Mary's Hospital, Paddington the same hospital in which Prince William and his brother, Prince Harry, were born to Diana, Princess of Wales, in 1982 and 1984, respectively. . . . #HappyBirthday #PrinceGeorge #PrinceGeorgeofCambridge #royalty #Royalfamily #HouseofWindsor #BritishMonarchy
It feels like just yesterday we were all staring at those Lindo Wing doors at St Mary's Hospital in London, waiting for the new royal baby to make his first public appearance. That was on July 22, 2013.
George is the first child of The Duke and Duchess of Cambridge and his full title is HRH Prince George Alexander Louis of Cambridge and he's third in line to the throne after granddad Prince Charles and dad William.
He was born at 4.24pm and weighed 8lbs 6oz.
When Kate went into labour on the morning of 22 July the entire world was holding its breath waiting for news of the new arrival.
The royal couple didn't learn their child's sex ahead of the birth.
The birth of a royal baby is traditionally announced via an easel placed outside Buckingham Palace. The medical staff sign an official birth announcement that is taken by a royal aide - via police escort - to the palace where it is attached to an easel for the public to see.
But in a break from tradition, George's arrival was announced by a press release, before the royal birth announcement was taken from the hospital to the palace where it was then displayed on an easel in the palace's forecourt.
Media and hundreds of well wishers had been camped outside the hospital awaiting the announcement and that first glimpse of baby George, which happened the following evening.
Dressed in a blue polka dot dress, Kate emerged from the hospital holding her baby son – then unnamed – who was wrapped in a white blanket. She then handed him to William before they placed him in a car seat and drove back to Kensington Palace.
It feels like yesterday!
They announced his name on 24 July. (FYI: Reveal readers had voted George as their baby name of choice for the newborn!)
Happy birthday to Prince George!