The National Trust, formally the National Trust for Places of Historic Interest or Natural Beauty, is a charity and membership organisation for heritage conservation in England, Wales and Northern Ireland. In Scotland, there is a separate and independent National Trust for Scotland.

The Trust was founded in 1895 by Octavia Hill, Sir Robert Hunter and Hardwicke Rawnsley to "promote the permanent preservation for the benefit of the Nation of lands and tenements (including buildings) of beauty or historic interest". It was given statutory powers, starting with the National Trust Act 1907. Historically, the Trust acquired land by gift and sometimes by public subscription and appeal, but after World War II the loss of country houses resulted in many such properties being acquired either by gift from the former owners or through the National Land Fund. Country houses and estates still make up a significant part of its holdings, but it is also known for its protection of wild landscapes such as in the Lake District and Peak District. As well as the great estates of titled families, it has acquired smaller houses including some whose significance is not architectural but through their association with famous people, for example, the childhood homes of John Lennon and Paul McCartney.

One of the largest landowners in the United Kingdom, the Trust owns almost 250,000 hectares (620,000 acres; 2,500 km²; 970 sq mi) of land and 780 miles of coast. Its properties include over 500 historic houses, castles, archaeological and industrial monuments, gardens, parks and nature reserves. Most properties are open to the public for a charge (members have free entry), while open spaces are free to all. The Trust has an annual income of over £680 million, largely from membership subscriptions, donations and legacies, direct property income, profits from its shops and restaurants, and investments. It also receives grants from a variety of organisations including other charities, government departments, local authorities and the National Lottery Heritage Fund.