The destruction of country houses in 20th-century Britain was the result of a change in social conditions: many country houses of varying architectural merit were demolished by their owners. Collectively termed by several authors "the lost houses", the destruction of these now often-forgotten houses has been described as a cultural tragedy.

An English country house is a large house or mansion in the English countryside. Such houses were often owned by individuals who also owned a town house. This allowed them to spend time in the country and in the city—hence, for these people, the term distinguished between town and country. However, the term also encompasses houses that were, and often still are, the full-time residence for the landed gentry who dominated rural Britain until the Reform Act 1832. Frequently, the formal business of the counties was transacted in these country houses, having functional antecedents in manor houses.