Greek National Road 3 (, abbreviated as EO3) is a single carriageway road in  Greece. It connects Eleusis near Athens with the border of the Republic of Macedonia at Niki. It passes through Larissa and Florina. At Niki it connects with the M5K motorway to Bitola. Greek National Road 3 is one of the longest highways in Greece and up until the 1960s it served as the main route from Larissa to Thessaloniki. The new A1 motorway now offers a faster connection to Thessaloniki. Most of the EO3, except the southernmost section between Eleusis and Bralos, is part of the E65.