Chelsea FC is an English football club, based in the London borough of Kensington and  Chelsea. Chelsea were founded on 10 March 1905 at The Rising Sun pub (now The Butcher's Hook) opposite the present-day main entrance to the ground on Fulham Road, and were elected to the Football League shortly afterwards. The club owe their existence to that fact that Fulham turned down an offer of the use of the athletics stadium at Stamford Bridge, prompting the owner to form a new club to use the facilities there. The club's early years saw little success; the closest they came to winning a major trophy was reaching the FA Cup final in1915 which they lost to Sheffield United. Chelsea gained a reputation for signing big-name players and for being entertainers but made little impact on the English game in the inter-war years. Former Arsenal and England centre-forward Ted Drake became manager in 1952 and proceeded to modernize the club. He removed the club's Chelsea pensioner crest, improved the youth set-up and training regime, rebuilt the side, and led Chelsea to their first major trophy success – the League championship – in 1954–55. The 1960s saw the emergence of a talented young Chelsea side under manager Tommy Docherty. They challenged for honours throughout the decade, and endured several near-misses. 

Chelsea finally won the FA Cup in 1970, beating Leeds United 2–1 in a final replay. They  took their first European honour, a UEFA Cup Winners' Cup triumph, the following year with another replay win this time over Real Madrid in Athens.  The late 1970s through to the 1980s was a turbulent period for Chelsea. An ambitious redevelopment of Stamford Bridge threatened the financial stability of the club, star players were sold and the team was relegated. It was not until the appointment of former European Footballer of the Year Ruud Gullit as player-manager in 1996 that their fortunes changed. He added several top-class international players to the side, as the club won the FA Cup in 1997 and established themselves as one of England's top sides again. Gullit was replaced by Gianluca Vialli, who led the team to victory in the League Cup and the Cup Winners' Cup in 1998, the FA Cup in 2000 and the UEFA Champions League quarter-finals in 2000. Vialli was sacked in favour of another Italian, Claudio Ranieri, who guided Chelsea to the 2002 FA Cup Final and Champions League qualification in 2002–03.In June 2003, Bates sold Chelsea to Russian billionaire Roman Abramovich for £140 million, completing what was then the biggest-ever sale of an English football club. Over £100 million was spent on new players, but Ranieri was unable to deliver any trophies, so he was replaced by Portuguese coach José Mourinho. Under Mourinho, Chelsea became the fifth English team to win back-to-back league championships since the Second World War (2004–05 and 2005–06), in addition to winning an FA Cup (2007) and two League Cups (2005 and 2007). In September 2007 Mourinho was replaced by Avram Grant who led the club to their first UEFA Champions League final which they lost on penalties to Manchester United. Grant was sacked days later and succeeded by Luiz Felipe Scolari in July 2008. Scolari spent only seven months in the job before being dismissed after a string of poor results. Russia coach Guus Hiddink was appointed caretaker manager until the end of the 2008–09 season and secured a 2–1 win over Everton in the FA Cup Final. Two days later former AC Milan coach Carlo Ancelotti was confirmed as Chelsea's new manager and guided them to the League Championship and FA Cup double.  He was sacked at the end of the following season when he failed to secure any silverware.  

New manager André Villas-Boas lasted to the following March 2012 when he parted with the club after a poor run of results and former Chelsea player Roberto Di Matteo was appointed as interim first team manager. In a remarkable end to a season of poor performances, Chelsea defeated Liverpool 2-1 in the FA Cup Final and defeated Bayern Munich in their own ground on penalties in the Champion’s League Final.  A poor start the following seasons, led to the sacking of Di Matteo. Rafa Benítez made a surprise return to English football as caretaker manager of Chelsea guiding them to victory in the 2012/13 Europa Cup Final only British club, to have won all three of UEFA's major club competitions.  The return of fan’s favourite Jose Mourinho in 2013-14 promised more success in the future. He one the league title the following year, but turmoil on and off the pitch led to a tenth place finish in 2015-16 and Mourinho’s departure before the end of the season. His replacement Antonio Conte won the title in his first season but, despite winning the FA Cup, failure to secure a champions league place the following season saw him part company with the club.He was replaced with Maurizio Sarri under whom Chelsea reached the League Cup final, which they lost on penalties to Manchester City and won the Europa League for a second time, beating Arsenal 4–1 in the final. Sarri then left the club to become manager of Juventus and was then replaced by former Chelsea player Frank Lampard. In Lampard's first season he guided Chelsea to foutth place in the Premier League and reached the FA Cup final, losing 2–1 to Arsenal.Lampard was dismissed in January 2021 and replaced with Thomas Tuchel. Under Tuchel, Chelsea reached the FA Cup final, losing 1–0 to Leicester City, and won their second UEFA Champions League title with a 1–0 win over Manchester City in Porto.A 3rd place finishing in the league the following seasons and two cup finals (both ending in defeat) and a summer spend of £250 million, failed to keep Tuchel in his job beyond  September 2022. His replacement Graham Potter was sacked in April 2023 and Chelsea finished in the bottom half of the league for the first time since 1996.