Barkley made 100 Chelsea appearances and scored 12 goals following his switch from Everton in January 2018.
Barkley struggled to replicate his impact at boyhood club Everton in west London, finding his first-team chances increasingly limited in the last two seasons.
Chelsea's new owners have continued their progressive approach to reshaping the Blues' senior squad this summer by agreeing a deal for Barkley to leave Stamford Bridge, despite his contract not expiring until next summer.
Barkley's best moment at the Blues came in his substitute appearance in the 4-1 Europa League final triumph over Arsenal in Baku in 2019.
"Ross Barkley has left Chelsea by mutual consent and becomes a free agent," read a Chelsea statement.
"The midfielder, who joined from boyhood club Everton in January 2018, made 100 appearances for the Blues in all competitions, scoring 12 goals.
"The most memorable was his injury-time equaliser against Manchester United in his first full season at the Bridge.
"At the end of that campaign he helped win the Europa League, scoring a spot kick in the shoot-out victory over Eintracht Frankfurt in the semis and then coming off the bench in the brilliant Baku triumph against Arsenal."