This list of castles in England is not a list of every building and site that has "castle" as part of its name, nor does it list only buildings that conform to a strict definition of a castle as a medieval fortified residence.[1] It is not a list of every castle ever built in England, many of which have vanished without trace, but is primarily a list of buildings and remains that have survived. In almost every case the buildings that survive are either ruined, or have been altered over the centuries. For several reasons, whether a given site is that of a medieval castle has not been taken to be a sufficient criterion for determining whether or not that site should be included in the list.
Castles that have vanished or whose remains are barely visible are not listed, except for some important or well-known buildings and sites. Fortifications from before the medieval period are not listed, nor are architectural follies. In other respects it is difficult to identify clear and consistent boundaries between two sets of buildings, comprising those that indisputably belong in a list of castles and those that do not. The criteria adopted for inclusion in the list include such factors as: how much survives from the medieval period; how strongly fortified the building was; how castle-like the surviving building is; whether the building has been given the title of "castle"; how certain it is that a medieval castle stood on the site, or that the surviving remains are those of a medieval castle; how well-known or interesting the building is; and whether including or excluding a building helps make the list, in some measure, more consistent.
In order to establish a list that is as far as possible comprehensive as well as consistent, it is necessary to establish its boundaries. Before the list itself, a discussion of its scope includes lengthy lists of buildings excluded from the main lists for various reasons. The Castellarium Anglicanum, an authoritative index of castles in England and Wales published in 1983, lists over 1,500 castle sites in England.[2] Many of these castles have vanished or left almost no trace. The present list includes more than 800 medieval castles of which there are visible remains, with over 300 having substantial surviving stone or brick remains.