The royal baby was born Monday at 4:24 p.m. London time, weighing 8 pounds 6 ounces. The name has not yet been revealed.
William and Kate entered St. Mary's through a side door earlier Monday morning, avoiding the world's media. Royal officials said they traveled by car, without a police escort, just before 6 a.m. Palace officials confirmed her arrival about 90 minutes later.
Kate — also known as the Duchess of Cambridge — gave birth in the private Lindo Wing of the hospital, where Princess Diana also gave birth to William and his younger brother, Prince Harry.
She was looked after by a top-notch medical team led by royal gynecologist Dr. Marcus Setchell.
The baby is in line to become Britain's monarch and be recognized as head of state in 15 other countries, including Canada and Australia, playing a leading role in charting the future of the Commonwealth.