The municipality of Guidonia Montecelio, formed by the main towns of Guidonia and Montecelio, lies to the north-east of Rome, some kilometres from the Grande Raccordo Anulare - a ring-shaped motorway which forms a circle around the capital.
It borders with Fonte Nuova, Marcellina, Palombara Sabina, Rome, San Polo dei Cavalieri, Sant'Angelo Romano and Tivoli.