The couple, who met more than eight years ago while attending the University of St. Andrews in Scotland, got engaged last month during a vacation in Kenya.
The 28-year-old prince is second in line to the throne after his father, Prince Charles. Middleton, also 28, is the daughter of self-made millionaires and works for the family mail-order business, which specializes in children's parties.
The couple will live in north Wales following their marriage, where Prince William will continue to serve with the Royal Air Force, according to royal officials.
William's grandparents, Queen Elizabeth II and Prince Philip, "are absolutely delighted for them both," Buckingham Palace said.