The heir to the throne, William Arthur Philip Louis, was born 21 June 1982,  the elder son of HM King Charles III, and the late Diana, Princess of Wales.

The young prince made his first public appearance, aged nine, when he accompanied his parents on an official visit to Cardiff. He was educated at Ludgrove preparatory school, before going to Eton, where he studied biology, geography and art history at A-level.

Diana, Princess of Wales was determined that both her sons should have as 'normal' a childhood as possible and tried to give them a range of experiences – from rides on the big dippers at theme parks and trips to McDonald's, to accompanying her on her official visits to AIDS wards and homeless shelters.

William's most memorable public appearance as a teenager was at the funeral of his mother in September 1997 after she had died in a car crash in Paris. Along with his father, grandfather and younger brother, the 15-year-old prince walked behind the funeral cortege as it made its way through central London, enduring intense public scrutiny at a time of private grief.

William's gap year activities included a spell with the British Army in Belize and ten weeks in Chile, where he taught children as part of a Raleigh International programme. He then went on to St Andrews University to study Art History, later changing his degree to Geography. He graduated with an upper second-class honours degree in 2005.

William graduated from Sandhurst Military Academy in 2006 and, as Lieutenant William Wales, entered the Blues and Royals as a troop commander in an armoured reconnaissance unit.

Although William wanted to see active service, government ministers advised that his personal security should be safeguarded. Instead, he went on to train in the Royal Navy and the RAF. William decided to extend his original three-year contract with the armed forces and in January 2009 began training as a helicopter pilot with the RAF Search and Rescue Force. He graduated in September 2010 and started working as part of a four-man crew based at RAF Valley in Anglesey on the north west coast of Wales with the rank of Flight Lieutenant. In 2013 he left the armed services and in 2014 started a short course in land management at Cambridge, with a view to being more actively involved with the Duchy of Cornwall, as well as taking on more royal duties. In Autumn 2014 Prince William began six months' training for his new job as a pilot with the East Anglian Air Ambulance, which involved acquiring a civil pilot's licence. The Prince donated his salary to charity.

During his time at St Andrews, William met a fellow student, Catherine Middleton, known popularly as Kate. In June 2008 Middleton attended William's investiture into the Order of the Garter with other members of the royal family. On 16 November 2010 Clarence House announced their engagement.

On 29 April 2011, in front of a worldwide television audience of two billion, Prince William married Catherine (Kate) Middleton, in Westminster Abbey.

On the morning of the wedding, Buckingham Palace released a statement to say that Queen Elizabeth II had created her grandson, Prince William of Wales, Duke of Cambridge. The title also has lesser (or subsidiary) titles, in this case Earl of Strathearn and  Baron Carrickfergus. 

On 8 September 2022, Prince William inherited many of his father's titles, as heir to the throne.  On 9 September 2022 in  his first address to the nation, King Charles III declared that his son would be Prince of Wales. The correct forms of address for William and Catherine are now His Royal Highness The Prince of Wales and Her Royal Highness Catherine, The Princess of Wales.

The Prince and Princess of Wales have three children: George Alexander Louis, born 22 July 2013; Charlotte Elizabeth Diana, born 2 May 2015; Louis Arthur Charles, born 23 April 2018.

William undertook his first independent overseas tour in 2005, when he travelled to New Zealand to participate in World War II commemorations. He has been involved in charity work since an early age and is patron of a number of charities, including the homeless charity Centrepoint, the Royal Marsden Hospital and Mountain Rescue England and Wales. He is also a patron of Tusk Trust, a wildlife conservation organisation based in Africa, and The Queen Elizabeth II Fields, an initiative of the Fields Trust. 

To further their charitable work, Prince Harry and Prince William created their own Foundation in 2009, now called the Royal Foundation. The Duchess of Cornwall and Cambridge also became a Patron in 2011, and the Duchess of Sussex in 2018.

The Foundation launched the Heads Together campaign in 2017, which partnered with eight mental health charities to open up the conversation surrounding mental health and to provide help to those suffering from mental health problems such as depression, PTSD, anxiety and loneliness.

The Prince and Princess of Wales, along with Prince Harry, were Official Ambassadors for Team GB and Paralympics GB for the 2012 Olympic and Paralympic Games.

William enjoys sport and, like his father, is a keen polo player, although he now mainly plays in exhibition matches for good causes. He is also the vice-patron of the Welsh Rugby Union, and an enthusiastic football fan, who supports Aston Villa and is President of the Football Association (FA).

In 2022, the Prince and Princess of Wales, Prince George, Princess Charlotte and Prince Louis moved from Kensington Palace to Windsor; they also have  a country house, Anmer Hall, on The King's Sandringham estate in Norfolk.