Iran has dropped espionage charge against French-Iranian academic Fariba Adelkhah, who has been detained in the country since June last year.
Her lawyer, Said Dehghan, welcomed the decision to lift the charge, which carries the death penalty.
Ms Adelkhah still faces two charges: spreading "propaganda against the political system" of Iran and "conspiracy against national security".
Mr Dehghan said the prosecution dropped its case against her for "disturbing the public order".
Ms Adelkhah is a research director at Sciences Po University in Paris, specialising in the study of Shiite Islam. Her arrest on suspicion of espionage was confirmed on July 16 by Iran's judicial spokesman Gholamhossein Esmaili.
Her colleague Roland Marchal was arrested while visiting Ms Adelkhah, his lawyer said.
Sciences Po University and supporters said last month that Ms Adelkhah and another detained academic, Australian Kylie Moore-Gilbert, started an indefinite hunger strike before Christmas.
Last month France said it summoned Iran's ambassador to protest against the imprisonment of the academics, calling their detention "intolerable".
France said the ambassador was informed of "our grave concern over the situation of Fariba Adelkhah, who has stopped taking food".
Tehran, which does not recognise dual nationalities, has criticised Paris for "unacceptable interference" in its domestic affairs after the French government sought consular access to Ms Adelkhah.