The Twentieth Century Society is a British charity which campaigns for the preservation of architectural heritage from 1914 onwards. The society's interests extend to buildings or artefacts, whether important or humble, rare or commonplace, that characterise Twentieth Century Britain.
The Sociey was formed as The Thirties Society in 1979, the year in which the Thirties exhibition was shown at the Hayward Gallery. The idea came from The Victorian Society which aims to protect pre-1914 Victorian and Edwardian buildings. Though several modern buildings had been listed on the recommendation of Nikolaus Pevsner in 1970, it was felt by John Harris and Sir Simon Jenkins that much more needed to be done. Bevis Hillier was the first president, Clive Aslet the first honorary secretary. In 1992 it changed its name to The Twentieth Century Society as it was felt that Thirties Society was a poor description as the society aimed to protect buildings from other periods as well.