Campo Marzio (Italian: [ˈkampo ˈmartsjo]) is the 4th rione of Rome, Italy, identified by the initials R. IV. It belongs to the Municipio I and covers a smaller section of the area of the ancient Campus Martius. The logo of this rione is a silver crescent on a blue background.
Santa Maria in Montesanto is a titular minor basilica church in Rome, in the Rione Campo Marzio, which stands in Piazza del Popolo, between Via del Corso and Via del Babuino. It is also known as the Church of the Artists (Chiesa degli artisti). The church is popularly known as the twin church of Santa Maria dei Miracoli, though it shows significant differences especially in the planimetry.
The Campus Martius (Latin for 'Field of Mars'; Italian: Campo Marzio) was a publicly owned area of ancient Rome about 2 square kilometres (490 acres) in extent. In the Middle Ages, it was the most populous area of Rome. The IV rione of Rome, Campo Marzio, which covers a smaller section of the original area, bears the same name.