ATAC Company for the Mobility of Rome Capital is a public Italian transport company entirely controlled by Rome Capital that manages under concession a large part of the local public transport and related integrated services of Rome, extending in part to some municipalities of the metropolitan city.

ATAC is one of the largest transport service providers in Italy and Europe: under in-house providing, it manages 80% of the urban bus network as well as the trolleybus, metro, and tram networks, in addition to the Rome-Giardinetti railway. It operates both as a railway company and as an infrastructure manager, also taking care of the management of paid parking and interchange, and has a bus rental service with driver, mainly for tourism, and historic trams.

ATAC was founded as the Municipal Autonomous Tramway Company in 1909 as part of the municipalization of capital services for the management of the automotive and tram networks of Rome in open competition with the private company SRTO, from which it progressively absorbed resources and managed services.