Here is everything we know about him so far:
He’s is healthy and happy
Palace officials announced that the future king was born at 16:24, weighing 8 pounds, 6 ounces (3.75kg), at central London's St Mary's Hospital — the same place where William and his brother Harry were born three decades ago.
The newborn Prince spent his first night in hospital with both his mom the Duchess of Cambridge and his dad, Prince William.
He has a title but no name
Although the little one has no name yet, he already has a title. He will be referred to as HRH Prince of Cambridge.
"The name of the baby will be announced in due course," Kensington Palace said in a statement. Will and Kate will decide when to make the announcement. Prince William's own parents, Prince Charles and the late Princess Diana, waited a week before announcing his name.
The new prince is now third in line to the throne behind his grandfather, Prince Charles, and his dad, Prince William, bumping uncle Prince Harry down to number four.
When it comes to the royal baby, choosing just one name won't do. You need about three or four.
Just ask the father, William Arthur Philip Louis. Or the grandfather, Charles Philip Arthur George. Or the great-grandmother, Elizabeth Alexandra Mary.
"I think because the child is going to be the third in line to the throne, they have to maintain all this tradition," said Pauline MacLaran, a professor of marketing and consumer research at Royal Holloway and the co-author of the upcoming book, "Royal Fever: The British Monarchy in Consumer Culture”.
"They'll go for three or four names and ... be able to make the right nod to the right people," she said.
He can choose his surname
The royal baby's last name could be one of three choices: Wales, like dad; Cambridge, like the royal house bestowed on his parents by Queen Elizabeth when they got married; or Mountbatten-Windsor, the two-for-one surname of Prince Philip, who got Mountbatten for his maternal grandparents, and the queen, whose father, King George V, selected Windsor for his family in 1917.
His star sign:
Britain's new baby Prince follows his father and late grandmother by being born under the zodiac sign of Cancer, suggesting he will be a strong leader, according to astrologists.
But the crab was almost a lion, having been born just 30 minutes before the sun entered the Leo constellation.
The baby's father, Prince William, was born on June 21 and is also a Cancerian, as was William's mother Princess Diana, whose birthday was July 1.
Cancerians are renowned by astrologists to be protective and emotional, given that they are supposedly ruled by the moon, but are quick to retreat back within their shell.
However, astrologer
Patrick Arundell also explained that the baby's birth sign would give
him "regal power" and a "very special aura".