Mega Dereio (Greek: Μέγα Δέρειο) is a village in the central part of the Evros regional unit in Greece.

It is situated near the upper course of the river Erythropotamos, in the Eastern Rhodope Mountains.

The Greek National Road 53 (Alexandroupoli – Mikro Dereio – Kyprinos – Ormenio) passes through the village.

[3] In August 1913 the village was attacked by Turkish troops and irregulars and despite the resistance of the local Bulgarians the bigger part of Golyam Dervent was burned.

As a result its Bulgarian and Turkish population was exchanged with Greek refugees, mainly from today's Turkey.