This article is about the 11th century census. See BBC Domesday Project for the multimedia project and Doomsday Book (novel) for the Connie Willis novel.

The Domesday Book (also known as Domesday, or Book of Winchester) was the record of the great survey of England completed in 1086, executed for William I of England. The survey was similar to a census by a government of today. William needed information about the country he had just conquered so he could administer it. While spending Christmas of 1085 in Gloucester, William "had deep speech with his counsellors and sent men all over England to each shire ... to find out ... what or how much each landholder had in land and livestock, and what it was worth." (Anglo-Saxon Chronicle)

One of the main purposes of the survey was to find out who owned what so they could be taxed on it, and the judgment of the assessors was final—whatever the book said about who owned the property, or what it was worth, was the law, and there was no appeal. It was written in Latin, although there were some vernacular words inserted for native terms with no previous Latin equivalent and the text was highly abbreviated. The name Domesday comes from the Old English word dom, meaning accounting or reckoning. Thus domesday, or doomsday, is literally a day of reckoning, meaning that a lord takes account of what is owed by his subjects. Medieval Christians believed that in the Last Judgment as recorded in Revelation, Christ would carry out a similar accounting of one's deeds—hence the term doomsday also referred to this eschatological event.

In August 2006, a complete online version of Domesday Book was made available for the first time by the UK's National Archives.