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.

Athens is the capital and largest city of Greece. A major coastal urban area in the Mediterranean, Athens is also the capital of the Attica region and is the southernmost capital on the European mainland. With its urban area's population numbering over three million, it is the eighth largest urban area in the European Union. The Municipality of Athens, which constitutes a small administrative unit of the entire urban area, had a population of 643,452 (2021) within its official limits, and a land area of 38.96 km2 (15.04 sq mi).