Elliniko Metro, formerly Attiko Metro until May 2023, is a Greek State-owned company who is responsible for the development and construction of the Athens Metro and the Thessaloniki Metro, as well as the Athens Tram.

The Athens Metro is a rapid-transit system in Greece which serves the Athens urban area. Line 1 opened as a single-track conventional steam railway in 1869 and was electrified in 1904. Beginning in 1991, Elliniko Metro S.A. constructed and extended Lines 2 and 3. It has significantly changed Athens by providing a much-needed solution to the city's traffic and air pollution problem, as well as revitalising many of the areas it serves. Extensions of existing lines are under development or tender, like the Line 2 extension to Ilion where tender started in 2023, as well as a new Line 4, whose central section began construction in October 2021. The Athens Metro is actively connected with the other means of public transport, such as buses, trolleys, the Athens Tram and the Athens Suburban Railway. The Athens Metro is hailed for its modernity, and many of its stations feature works of art, exhibitions and displays of the archaeological remains found during its construction. Photography and video-taking is permitted across the whole network and street photographers often work in Athens Metro. This will be the only metro system in Greece, until the Thessaloniki Metro begins operation in 2024.