Chelsea Football Club are a professional football club based in Fulham, London, who play in the Premier League, the highest level of English football. Founded in 1905, the club have spent most of their history in the top tier of English football. The club's home ground is the 41,837-seat Stamford Bridge stadium, where they have played since their establishment.

One of the most successful clubs in English football, Chelsea had their first major success in 1955, when they won the league championship, and subsequently won various cup competitions between 1965 and 1990. The club have enjoyed their greatest period of success in the past two decades, winning 17 major trophies since 1997.

Domestically, Chelsea have won five league titles, seven FA Cups, five League Cups and four FA Community Shields, while in continental competitions they have won one UEFA Champions League, two UEFA Cup Winners' Cups, one UEFA Europa League and one UEFA Super Cup. Chelsea are the only London club to win the UEFA Champions League, and one of four clubs, and the only British club, to have won all three main UEFA club competitions.

Chelsea's regular kit colours are royal blue shirts and shorts with white socks. The club's crest has been changed several times in attempts to re-brand the club and modernise its image. The current crest, featuring a ceremonial lion rampant regardant holding a staff, is a modification of the one introduced in the early 1950s. The club have sustained the fifth-highest average all-time attendance in English football. Their average home gate for the 2013-14 season was 41,572, the seventh highest in the Premier League. Since July 2003, Chelsea have been owned by Russian billionaire Roman Abramovich. In May 2015 they were ranked by Forbes Magazine as the sixth most valuable football club in the world, at £898 million ($1.37 billion).