Spare is a memoir by Prince Harry, Duke of Sussex, which was released in 2023. It was ghostwritten by J. R. Moehringer and published by Penguin Random House. An audiobook edition is narrated by Harry.

The book was highly anticipated and was accompanied by several major broadcast interviews. The title refers to the aristocratic adage that an "heir and a spare" were needed to ensure that an inheritance remained in the family. In the book, Harry details his childhood and the profound effect of the death of his mother, Diana, Princess of Wales, as well as his teenage years, and subsequent deployment to Afghanistan with the British Army. He writes about his relationship with his older brother, Prince William, and his father, King Charles III, and his father's marriage to Queen Camilla, as well as his courtship and marriage to the American actress Meghan Markle and the couple's subsequent stepping back from their royal roles.

Spare received generally mixed reviews from critics, some who praised Harry's openness but were critical of the inclusion of too many personal details. According to Guinness World Records, Spare became "the fastest selling non-fiction book of all time" on the date of its release.

In July 2021, it was announced that Harry was set to publish a memoir via Penguin Random House, with proceeds from its sales going to charity and Harry reportedly earning an advance of at least $20 million. It is ghostwritten by journalist J. R. Moehringer. In the following month, he confirmed that $1.5 million of the proceeds from the memoir would go to the charity Sentebale, while £300,000 would be given to WellChild.

In the summer of 2021, Harry stated: "I'm writing this not as the prince I was born but as the man I have become. I've worn many hats over the years, both literally and figuratively, and my hope is that in telling my story – the highs and lows, the mistakes, the lessons learned – I can help show that no matter where we come from, we have more in common than we think." Harry said the book was "accurate and wholly truthful". The publisher stated that the book takes readers "immediately back to one of the most searing images of the 20th century: two young boys, two princes, walking behind their mother's coffin as the world watched in sorrow – and horror." The publisher maintained the book is "full of insight, revelation, self-examination, and hard-won wisdom."

The Times reported in January 2023 that Harry had second thoughts about publishing the book after visiting his grandmother Queen Elizabeth II during her Platinum Jubilee celebrations in the summer of 2022, but eventually went ahead with it. In an interview with Bryony Gordon, he stated that the first draft was 800 pages, meaning that he had enough material for two books, but it was reduced to about 400 pages because there were things between him and his father and brother "that I just don't want the world to know. Because I don't think they would ever forgive me." He claimed that the book's aim was "not trying to collapse the monarchy" but rather save it, and added that he felt he had an obligation to reform the institution for the sake of future spares, namely his brother's younger children, despite being told explicitly by William that his children are not Harry's responsibility.

The book is Harry's account of his life to date. The title is a reference to the aristocratic adage that an "heir and a spare" were needed to ensure that the inheritance remained in the family if anything happened to the heir. The book is an autobiography, but he begins near the end, describing a meeting with his father and brother to discuss his plan to step back from his royal role. He then focuses on his education, his time in the British Army, and his relationship with his family and with his wife, Meghan.

Harry describes his understanding of the role of "Spare" and his acceptance of it: