The Thessaloniki Metro is an underground rapid-transit system under construction in Thessaloniki, Greece's second largest city. Estimates for the cost of the megaproject are €1.62 billion ($1.83 billion) for the main line and €640 million ($723 million) for the Kalamaria extension, for a total of €2.26 billion ($2.55 billion). The project is primarily funded with loans from the European Investment Bank (EIB) and the European Regional Development Fund (ERDF) and funds from the Greek government. Construction by a Greek-Italian consortium is overseen by Elliniko Metro S.A., the Greek state-owned company which oversaw construction of the Athens Metro and Athens Tram.

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.