Chelsea Football Club (also known as The Blues or previously The Pensioners) are a professional English football club based in west London. Founded in 1905, they play in the Premier League and have spent most of their history in the top tier in English football. They have had two broad periods of success, one during the 1960s and early 1970s, and the second from the late 1990s to the present day. Chelsea have won three league titles, four FA Cups, four League Cups, two UEFA Cup Winners' Cups, and have reached one UEFA Champions League final.

Chelsea's home is the 42,055-person capacity Stamford Bridge football stadium in Fulham, West London, where they have played since their establishment. Despite their name, the club are based just outside the Royal Borough of Kensington and Chelsea, in the London Borough of Hammersmith and Fulham. In 2003, the club was bought by Russian oil magnate Roman Abramovich.

The club's traditional kit colors are royal blue shirts and shorts with white socks. Their traditional crest is a ceremonial blue lion holding a staff; a modified version of this was adopted in 2005.