Ostia Antica is the 35th zona of Rome, Italy, four kilometers away from the coast. It is identified by the initials Z. XXXV and it is distinct from Ostia. Ostia Antica belongs to Municipio X.

Ostia is a large neighbourhood in the Municipio X of the comune of Rome, Italy, near the ancient port of Rome, which is now a major archaeological site known as Ostia Antica. Ostia is also the only municipio or district of Rome on the Tyrrhenian Sea, and many Romans spend the summer holidays there. Therefore it's entirely situated within the Municipality of Rome and is the city's seaside resort.