Greek National Road 8a (Greek: Εθνική Οδός 8a, abbreviated as EO8a) was a toll road in the Attica, Peloponnese and West Greece regions. It connected Athens with the cities of Corinth and Patras. It was built in the 1960s as a replacement for the old National Road 8 as the major route to the Peloponnese, and bypasses most towns. The National Road 8a has gradually been upgraded to a motorway, the A8. Since April 2017, the complete length of the A8 motorway has been operational.
The EO8a started east of Eleusis, where it branched off the old EO8 as a limited-access dual carriageway. Between Megara and Kineta the motorway passed through several tunnels. Its western end was the interchange with the A5 Ionia Odos, near Rio, northeast of Patras.