The Blues will not receive a transfer fee for the 34-year-old striker, who had just one year left on his contract at Stamford Bridge and was not wanted by manager Mauricio Pochettino.
The deal sees Aubameyang join his fourth club in just under 18 months having left Arsenal for Barcelona in February of last year.
After six fairly successful months at the Camp Nou, he was allowed to leave for Chelsea to reunite with Thomas Tuchel and lighten the Spanish giants’ wage bill.
However, Tuchel was sacked immediately after Aubameyang’s debut and he was used sparingly by both Graham Potter and Frank Lampard last season. In 21 appearances,he scored only three goals for the club.
Romelu Lukaku is also facing an uncertain future amid interest from Juventus and Al-Hilal in Saudi Arabia after Inter Milan pulled out of talks.