David Cameron and his wife Samantha wave to the world outside their new home. He's the youngest PM in nearly 200 years.
His full name is David William Duncan Cameron. He was born in London in 1966 - the third out of four children.
Here's the Prime Minister as a child. He was sent to boarding school aged 7.
He then went to Eton College, the same place that educated Princes William and Harry, as well as 18 other British Prime Ministers!
His biggest mention in the school magazine came when he sprained his ankle dancing to bagpipes on a school trip to Rome in Italy.
Here's the Cameron family out shopping in Portobello Market in London. Sadly, Ivan (on the left) died last year. Mrs Cameron is expecting their fourth child.
He supports Aston Villa, likes watching darts on telly and prefers snooker to pool.
His favourite music is Bob Dylan and indie rock such as The Killers, The Smiths, Radiohead and Pulp.
He was elected as an MP for the Conservatives in 2001. He represents the constituency of Witney in Oxfordshire.
Dogs pull Mr Cameron along the snow on a sled during a trip to Norway. He went to see the effects of climate change.
When he's not riding sleds, he's a keen cyclist and likes to get on his bike.
But he's been known to get the train too!
Newsround was one of his favourite programmes as a kid! Here he is with Leah and Press Packers Arian and Nivar. Looks like he and Leah are wearing matching outfits!