Lazio 1 is one of the 29 constituencies (Italian: circoscrizioni) represented in the Chamber of Deputies, the lower house of the Italian parliament.^[2] The constituency currently elects 39 deputies. Its boundaries correspond to those of the Metropolitan City of Rome, within the Lazio region. The electoral system uses a parallel voting system, which act as a mixed system, with 37% of seats allocated using a first-past-the-post electoral system and 61% using a proportional method, with one round of voting.^[3]

The constituency was first established by the Mattarella law on 4 August 1993 and later confirmed by the Calderoli law on 21 December 2005 and by the Rosato law on 3 November 2017.