Kate Middleton was born on 9 January 1982 at the Royal Berkshire Hospital, Reading, the daughter of Michael Francis Middleton and Carole Elizabeth. In 1987, the Middletons founded their own company, Party Pieces, a mail order firm that sells party paraphernalia. They have since become millionaires.

Middleton's status as the girlfriend of Prince William brought her widespread media coverage in the UK and abroad, and she was often photographed on her daily outings. On 17 October 2005, she complained through her lawyer about harassment from the media, stating that she had done nothing significant to warrant much publicity.

In February 2006, it was announced that Middleton would receive her own 24-hour security detail supplied by the Royalty and Diplomatic Protection Department. This fueled further speculation that she and Prince William would soon be engaged, since she would not, otherwise, be entitled to this service. No engagement occurred, and Middleton was not granted an allowance to fund this security. Middleton attended at least one event as an official royal guest, Prince William's "Passing-Out" parade at the Royal Military Academy Sandhurst on 15 December 2006.

On 14 April 2007 The Sun newspaper broke a 'world exclusive' suggesting that Prince William and Kate Middleton had split up. Other media outlets such as the BBC confirmed the story as the day progressed. The couple decided to break up during a holiday in the Swiss resort of Zermatt.

In June 2007, Middleton and Prince William insisted they were "just good friends" following reports of a reconciliation. Middleton and her family attended the Concert for Diana at Wembley Stadium; however, she and William sat two rows apart. Since then, the couple has been seen together in public on a number of occasions, and according to several news sources including the BBC and the Daily Mail, have now "rekindled their relationship". On 16 June 2008, Middleton attended the event of William's investment into the Order of the Garter along with the Royal Family.

In early 2006, it was rumoured that Middleton intended to found her own mail order company. However, a key investor stepped down, and Middleton decided to hold off on this plan. In November 2006, she accepted a position as an assistant accessories buyer with the British clothing chain Jigsaw. Prince William himself has stated that he does not intend to marry until he is at least 28 or at 30.

Middleton has also become known for her style and has been featured in numerous best dressed lists. Middleton was selected by The Telegraph as the "Most Promising Newcomer" in their 2006 list of style winners and losers. Tatler placed her at #8 on their yearly listing of the top ten style icons in 2007. She was also featured in People Magazine's 2007 best dressed list. Middleton was named as one of Richard Blackwell's ten "Fabulous Fashion Independents" of 2007. In June 2008 style.com selected Middleton as their monthly beauty icon. In July 2008 Middleton was named on Vanity Fair's international best dressed list.