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 weighed 3.8 kilograms . The palace says Kate and her child are both "doing well," and that they are staying in the hospital overnight.
Prince William said in a brief statement, "we could not be happier."
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."
"It has been a remarkable few years for our royal family, a royal wedding that captured people's hearts, that extraordinary and magnificent Jubilee and now this royal birth, all from a family that have given this nation so much incredible service, and they can know that a proud nation is celebrating with a very proud and happy couple tonight."
At Buckingham Palace, crowds cheered and rushed toward the gates as the news of the royal birth was announced. Many people stayed outside the palace late into the night.
The new baby will displace Prince Harry as third in line to the British throne, after Queen Elizabeth's eldest, Prince Charles, and his son, Prince William.
Soon after the royal birth, messages of congratulations began pouring in from around the world.
In a statement from the White House, U.S. President Barack Obama and first lady Michelle said they wished the couple "all the happiness and blessings parenthood brings."
Under a new law in Britain, still to be enacted by the country'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.