Final answer:
Prince William's full name is William Arthur Philip Louis, and he also holds the title of His Royal Highness The Duke of Cambridge.
Step-by-step explanation:
The full name of Prince William is William Arthur Philip Louis. He is the elder son of Charles, Prince of Wales, and Diana, Princess of Wales. As of the Royal Family's official website, his title is His Royal Highness The Duke of Cambridge.
He was given the Duke of Cambridge title upon his marriage to Catherine Middleton in 2011. This information is part of common knowledge regarding the British Royal Family, particularly for those interested in or studying modern British history and royal affairs.