Charlton Athletic Football Club is an English professional association football club based in Charlton, south-east London. They currently compete in League One, the third tier of English football, having been relegated from the Championship in the 2019–20 season. The club was founded on 9 June 1905 when a number of youth clubs in south-east London, including East Street Mission and Blundell Mission, combined to form Charlton Athletic. Their home ground is the Valley, where the club have played since 1919, apart from one year in Catford, during 1923–24, and seven years at Crystal Palace and West Ham United between 1985 and 1992, due to financial issues, and then safety concerns raised by the local council. The club's fans formed the Valley Party, nominating candidates to stand in local elections, in a bid to return the club to The Valley.
Charlton turned professional in 1920 and first entered the Football League in 1921. Since then the club has had four separate periods in the top flight of English football: 1936–1957, 1986–1990, 1998–1999, and 2000–2007. Historically, Charlton's most successful period was the 1930s, when the club's highest league finishes were recorded, including runners-up of the First Division in 1937. After World War II, Charlton reached two consecutive FA Cup finals, losing in 1946, and winning in 1947.
The club's traditional kit consists of red shirts, white shorts and red socks, and their most commonly used nickname is The Addicks. Charlton share local rivalries with fellow South London clubs Crystal Palace and Millwall.