The woman fell onto the tracks at around 11am as a train was approaching Lepanto station in the west of the city centre, and remained trapped under a carriage before emergency workers could free her.
She was brought out alive, according to reports, but died of her injuries shortly afterwards.
The station was evacuated and the line A closed between Termini, Rome's main train station, and Battistini, the final stop in the western suburbs. Replacement bus services are running along the route, which is the most used in Rome.
The eastern half of the line A is still operating but with delays, said public transport company Atac.
#info #atac – metro A: aggiornamento – interruzione TerminiBattistini. Attivo servizio di bus sostitutivi (accertamenti delle autorità dopo soccorso a persona sui binari). Circolazione attiva con rallentamenti tratta TerminiAnagnina. Seguono info #Roma #metroA
— infoatac (@InfoAtac) May 30, 2019
It's not clear what caused the woman, identified as a Senegalese national in her early 30s, to fall onto the tracks.
Authorities are reviewing CCTV footage to establish whether she could have slipped or been accidentally jostled by another passenger. A friend told Repubblica that she had sight problems that could have contributed to a fall.
The train driver is being treated for shock.