Line 1 of the Thessaloniki Metro, also known as the Base Project (Greek: Βασικό Έργο), is a deep-level underground rapid transit line in Thessaloniki, Greece, connecting New Railway Station in the west with Nea Elvetia in the east, before continuing on to the Pylaia.

The line opened on 30 November 2024.

[1] Discovery of historical sites in 2019 halted work for 28 months while excavations took place.

[2] Of the line's 13 stations, 11 are also stops for Thessaloniki Metro's Line 2, as they will share tunnels.

[3] Construction costs for the line are set at €1.05 billion ($1.19 billion), enough to classify it as a megaproject.