The son of an architect, Mark Haddon was born in Northampton, England in 1962 and studied English at Merton College, Oxford. He became a carer for disabled people in Scotland after university, an experience which would inform his later work. His first writing work was as a children's author and illustrator.
Haddon is most famous for his novel The Curious Incident of the Dog in the Night-time which won the Whitbread Book of the Year Award in 2003 and the Commonwealth Writers' Prize Overall Best First Book in 2004. This novel was the first Haddon wrote specifically for an adult audience, although it was eventually marketed to both adults and children. Haddon's earlier works include the children's series Agent Z. He also wrote the screenplay adaptation of Raymond Brigg's story Fungus the Bogeyman which was screened on BBC1 in 2004. In 2009 Haddon donated his short story The Island to Oxfam's 'Ox-Tales' project.
Haddon is a vegetarian as well as a hard line atheist who lives in Oxford with his wife, Dr. Sos Eltis, a Fellow of Brasenose College, and their two sons. He enjoys canoeing, cycling and running marathons.