The newborn baby girl made her first appearance to the public with the Duke of Cambridge and the Duchess outside St. Mary's Hospital on Saturday evening.
The baby, born at 8:34 a.m. local time (0734 GMT), was presented by her parents to the world at around 6:10 p.m.(1710 GMT).
The Duchess and the Duke of Cambridge looked very relax with smiles on their faces. The Duchess was taking the baby in her arm and the baby girl was asleep.
The couple didn't say anything in front of the media. But the Duke of Cambridge said he was "very happy" at the arrival of his second child when he went to Kensington Palace earlier this afternoon to take his son to the hospital.
The older brother Prince George has met his sister in the afternoon.
The royal family then left the hospital for Kensington Palace, which just needs a few minutes.
The baby weighs 8 lbs 3 oz, about 3.7 kg.
"Her Royal Highness and her child are both doing well," Kensington Palace said in a statement Saturday morning.
The newborn Princess is now the forth in line to the British throne, behind her brother George, father William and grandfather Prince Charles.
Credit: Xinhua