The 28-year-old royal - who is second in line to throne behind his father the Prince of Wales - will marry 28-year-old Kate next year following a secret engagement during a holiday to Kenya last month, Clarence House have confirmed.
A statement read: "The Prince of Wales is delighted to announce the engagement of PrinceWilliam to Miss Catherine Middleton.
"The wedding will take place in either spring or summer next year in London. Further details about the date and venue will be released in due course."
The pair began dating eight years ago while they both studied at St. Andrews University in Fife, Scotland.
William - the eldest son of Charles and the late Princess Diana - has previously revealed he planned to get married at the age of 28 or 29, although later said he regretted the statement.
He said: "I was young, I`d had a few drinks... what can I say? I wish I had kept my big mouth shut!"