British officials say Prince William's wife, Kate, has given birth to a baby boy, the couple's first child and the heir to the British throne.
In a statement, Kensington Palace said the boy was born Monday afternoon and weighs 3.8 kilograms .
The palace says Kate and her child are both "doing well," and that they will remain in the hospital overnight.
The Duchess of Cambridge was admitted to St. Mary's Hospital in central London early Monday, with hundreds of international media camped outside.
After the baby's birth, Prime Minister David Cameron called it an "important moment" for Britain. He said a "proud nation is celebrating."
At Buckingham Palace, crowds cheered and rushed toward the gates as the news of the royal birth was announced.
The child will displace Prince Harry as third in line to the British throne, after Queen Elizabeth's eldest, Prince Charles, and his son, Prince William.
Under a new law, still to be enacted by Britain's parliament, the child would have been heir to the throne even if it were a girl. For centuries, preference was given to male heirs, so a first-born princess could be overtaken in line by a younger brother.