Kate, the Duchess of Cambridge, has given birth to a baby girl, royal officials said Saturday.
Kensington Palace said a brief statement that Kate "was safely delivered of a daughter" at 8:34 a.m. London time (0734 GMT), less than three hours after she was admitted to a hospital.
The baby weighs 8 pounds 3 ounces (3.7 kg). The palace added that Kate and her child are both doing well, and that William was present for the birth.
The princess is fourth in line to the throne and the fifth great-grandchild of Queen Elizabeth II.
The statement said that senior royals have been informed, and "are delighted with the news."
Kate, who wed William in April 2011, gave birth to Prince George at the same hospital in July 2013.
Officials are not expected to announce the name of the newborn immediately. When George was born, officials waited two days before announcing his name.