The decision comes following Sunday's 3-1 league defeat to AC Milan and their Coppa Italia exit to rivals Lazio last Wednesday.
"We would like to thank Jose on behalf of all of us at AS Roma for his passion and efforts since his arrival at the club," a club statement read.
"We will always have great memories of his tenure at Roma, but we believe that an immediate change is in the best interests of the club.
"We wish Jose and his assistants all the best in their future endeavours."
Mourinho joined Roma in May 2021 and helped end the club's 11-year trophy drought by leading them to victory in the Europa Conference League in May 2022.
He led the Giallorossi to the Europa League final last season but they suffered a defeat on penalties to Sevilla, while their league form this term has slumped.
Roma have just one win in their last five games and have a Europa League knockout tie against Feyenoord next month.