Prime Minister David Cameron and his wife Samantha are celebrating the arrival of a baby girl.
It's their fourth child and she was born while the family was on holiday in Cornwall.
She's called Florence Rose Endellion Cameron. St Endellion is a village in the north of Cornwall.
The Camerons also have a six-year-old daughter called Nancy and a four-year-old son called Arthur. Their first child called Ivan died in 2009.
Mr Cameron is planning to take some time off running the country to help look after his new daughter.
His office said: "The prime minister and Mrs Cameron would like to thank the doctors and nurses at the hospital for their help and kindness."