American President Barack Obama has won the 2009 Nobel Peace Prize.
The judges said they'd given it to Mr Obama for "his extraordinary efforts to strengthen international diplomacy and co-operation between peoples".
There were a record 205 nominations for this year's prize, and Mr Obama wasn't among the favourites to win.
But the Nobel Committee said they wanted to support what he's trying to achieve, including working towards a world that's free of nuclear weapons.
The annual peace prize is named after Alfred Nobel, the Swedish inventor of dynamite.
When he died he left a large share of his money to be used for a series of prizes - the Nobel Prizes - one of which was for the person who's done the most to promote peace.
The winner, who's chosen by a group of five people - called the Nobel Committee - gets a gold medal, a diploma and prize money of 10m Swedish kronor - about £896,000!