Gabon striker Aubameyang, 33, scored 13 goals in 24 appearances for Barca after joining the Spanish club in February from Arsenal.
Former Barcelona forward, Pierre-Emerick Aubameyang has been signed by Chelsea.
Gabon striker Aubameyang, 33, scored 13 goals in 24 appearances for Barca after joining the Spanish club in February from Arsenal.
When Aubameyang signed for Barca he had a buyout clause of 100m euros (£83.4m) in his contract, but has only played eight minutes this season.
Barcelona have been looking to offload players after spending almost £200m on new arrivals despite being more than £1bn in debt.
The deal for Aubameyang means Chelsea chairman Todd Boehly has spent around £270m in his first transfer window since buying the club from Roman Abramovich - the highest amount any English club has spent in a single transfer window.
Aubameyang said: 'I'm really happy. It's an honour to be part of this team and I can't wait to start. I have some unfinished business with the Premier League so it's good to be back and really exciting.'
Only four players have scored more Premier League goals than Aubameyang's total of 68 in the period since 31 January 2018 - the date he joined Arsenal.
Aubameyang worked with Chelsea boss Thomas Tuchel at Borussia Dortmund between 2015 and 2017.
He scored 79 goals in 95 games under the German, 38 more than he netted under any other manager.