Chelsea Football Club (/ˈtʃɛlsiː/) are a professional football club based in Fulham, London, who compete in the Premier League. Founded in 1905, the club's home ground since then has been Stamford Bridge.

Chelsea had their first major success in 1955, when they won the league championship. They won various cup competitions between 1965 and 1990. The club's greatest period of success has been the last two decades, winning 17 major trophies since 1997. Chelsea have won five league titles, seven FA Cups, five League Cups and four FA Community Shields, 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 the fifth-highest average all-time attendance in English football. Their average home gate for the 2014–15 season was 41,546, the seventh highest in the Premier League. Since 2003, Chelsea have been owned by Russian billionaire Roman Abramovich. In 2015, they were ranked by Forbes magazine as the sixth most valuable football club in the world, at £898 million ($1.37 billion).