Because he is the son of the HRH the Prince of Wales he uses the name Prince William of Wales.
Wales
William Arthur Philip Louis of Wales
Technically HRH Prince William, Duke of Cambridge's last name is Mountbatten-Windsor, However he frequently uses Windsor or Wales
mountbatten Windsor
Wales is a principality, not a duchy. Prince Charles is the current Prince of Wales.
Prince Charles, Prince of Wales. Prince William of Wales. Prince Henry of Wales.
The name of Prince William's dad's name is Prince Charles who used to be married to Princess Diana the Princess who the world loved very much.
Williams last name came from Prince Williams
As members of the British Royal Family, they do not really have surnames. They can however be known as Mountbatten- Windsor (a combination of the Queen and Duke of Edinburgh's family names) or can take the surname 'Wales' due to their titles. For example, William's name within the RAF is William Wales.
The Father of Charles Prince of Wales is Queen Elizabeth II's Husband Prince Philip, Duke of Edinburgh
Williams last name came from Prince Williams
His full name is William Arthur Philip Louis.His official title is Prince William of Wales.