The pair will marry in the spring or summer of 2011, a statement from Clarence House, the prince's official residence, said.
The price, second in line to the throne, proposed during an October vacation to Kenya, the statement said.
"Prince William has informed The Queen and other close members of his family," the statement said. "Prince William has also sought the permission of Miss Middleton's father."
After they're married, the couple will live in north Wales, where Prince William is currently serving with the Royal Air Force.