Mikro Dereio () is a village and a community in the central part of the Evros regional unit in Greece. It is situated on the left bank of the river Erythropotamos, in the Eastern Rhodope Mountains. The border with Bulgaria is 5 km to the north. Mikro Dereio is on the Greek National Road 53. In 2011 its population was 158 for the settlement and 1,903 for the community, making it the most populous community of the municipal unit of Orfeas. The community consists of the villages Mikro Dereio, Geriko, Goniko, Mega Dereio, Petrolofos, Roussa and Sidirochori.