Sir Terence David John Pratchett OBE (28 April 1948 – 12 March 2015) was an English author, humorist, and satirist, best known for the Discworld series of 41 comic fantasy novels published between 1983 and 2015, and for the apocalyptic comedy novel Good Omens (1990), which he co-wrote with Neil Gaiman.

Pratchett's first novel, The Carpet People, was published in 1971. The first Discworld novel, The Colour of Magic, was published in 1983, after which Pratchett wrote an average of two books a year. The final Discworld novel, The Shepherd's Crown, was published in August 2015, five months after his death.

With more than 100 million books sold worldwide in 43 languages, Pratchett was the UK's best-selling author of the 1990s. He was appointed an Officer of the Order of the British Empire (OBE) in 1998 and was knighted for services to literature in the 2009 New Year Honours. In 2001, he won the annual Carnegie Medal for The Amazing Maurice and His Educated Rodents, the first Discworld book marketed for children. He received the World Fantasy Award for Life Achievement in 2010.

In December 2007 Pratchett announced that he had been diagnosed with early-onset Alzheimer's disease. He later made a substantial public donation to the Alzheimer's Research Trust (now Alzheimer's Research UK, ARUK), filmed three television programmes chronicling his experiences with the condition for the BBC, and became a patron of ARUK. Pratchett died on 12 March 2015, at the age of 66.

Pratchett was born on 28 April 1948 in Beaconsfield in Buckinghamshire, England, the only child of David (1921–2006), a mechanic, and Eileen Pratchett (1922–2010), a secretary, of Hay-on-Wye. His maternal grandparents came from Ireland. Pratchett attended Holtspur School, where he was bullied for his speech impediments. He was disliked by the head teacher, who, Pratchett said, thought "he could tell how successful you were going to be in later life by how well you could read or write at the age of six".

Pratchett's family moved to Bridgwater, Somerset, briefly in 1957. He passed his eleven plus exam in 1958, earning a place at High Wycombe Technical High School, where he was a key member of the debating society and wrote stories for the school magazine. Pratchett described himself as a "non-descript" student and, in his Who's Who entry, credited his education to the Beaconsfield Public Library.

Pratchett's early interests included astronomy. He collected Brooke Bond tea cards about space, owned a telescope and wanted to be an astronomer, but lacked the necessary mathematical skills. He developed an interest in science fiction and attended science fiction conventions from about 1963–1964, but stopped a few years later when he got his first job as a trainee journalist at the local paper. His early reading included the works of H. G. Wells, Arthur Conan Doyle, and "every book you really ought to read", which he later regarded as "getting an education".

Pratchett published his first short story, "Business Rivals", in the High Wycombe Technical School's magazine in 1962. It is the tale of a man named Crucible who finds the Devil in his flat in a cloud of sulphurous smoke. "The Hades Business" was published in the school magazine when he was 13, and published commercially when he was 15.