Movement for Change (KINAL) president Fofi Gennimata died on Monday at the age of 56.
The center-left leader, who had cancer, was admitted to the capital’s Evangelismos Hospital on October 12 after a relapse.
She was in the middle of a leadership race for the party, the third largest in Greece.
She died “after a years’ long battle and despite the efforts of her attending physicians,” the hospital’s administration said in a written statement on Monday, expressing its condolences to her family.
The mother of three was first diagnosed with breast cancer in 2008, at the age of 43.
Gennimata was elected in 2015 as the leader of the Panhellenic Socialist Movement (PASOK), which later became part of the center-left umbrella group Movement for Change.