The 34-year-old Ivory Coast international has spent eight years at Chelsea, scoring 157 goals in 341 appearances, and helped the Blues win 10 titles.
One of those titles was Saturday's Champions League victory over Bayern Munich, where Drogba scored a late equaliser in normal time and then netted the winning kick in the penalty shoot-out.
Drogba has been a talisman for Chelsea, spearheading their drive for success and delivering crucial performances in the matches which mattered most.
The former Marseille forward, who has been linked with a lucrative move to China, maintained Chelsea would "always be in my heart."
Drogba said on the club's official website, www.chelseafc.com: "I wanted to put an end to all the speculation and confirm that I am leaving Chelsea.
"It has been a very difficult decision for me to make and I am very proud of what we have achieved, but the time is right for a new challenge for me.
"As a team we have accomplished so much and have won every single trophy possible.
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"Saturday was a very special moment for everyone at the club and for all the fans, and I am very proud to have played my part in bringing many trophies to this club, which has been my home for the last eight years.
"I would like to take this opportunity to thank everyone at the club especially [owner] Roman [Abramovich] and my team-mates, many of whom have become very close friends and will be my friends for life.
"I would also like to say a very special thank you to the Chelsea fans who have shown me so much love and support over the years.
"I wish the club all the best and continued success for the future - you will always be in my heart."
Chelsea are set for some major decisions how to take the side forwards next season.
The Blues have yet to resolve firm plans for who will take charge of the team, with interim manager Roberto Di Matteo having done his claims for the full-time job no harm by following up an FA Cup final win at Wembley with landing the biggest prize of all following a penalty shoot-out in Munich.
Chelsea will wait until Di Matteo's contract expires at the end of June before deciding on the Italian's future, which could yet be back in the dugout on a one-year deal should owner Roman Abramovich put his faith in the man West Brom axed in February 2011 for fear of relegation.
Elsewhere, Chelsea also need to placate striker Fernando Torres, who hit out at his treatment last season, as well as look to secure their main transfer targets, said to include Lille playmaker Eden Hazard and Sao Paulo's Lucas Moura.
There could also yet be a return to the club for former striker Andriy Shevchenko. The 35-year-old is out to embark on a coaching career when he finally retires, which is likely to be after Ukraine host the European Championships this summer.