Methydrio (Greek: Μεθύδριο, before 1927: Νεμνίτσα - Nemnitsa) is a village in the municipal unit of Vytina, Arcadia, Greece. In 2001, it had a population of 14. It sits at 1,060 m above sea level, at the foot of the Mainalo mountains. It is 4 km south of Vytina. It was named after the ancient city Methydrion, the remains of which have been discovered near the village.
Ancient Methydrion was a city of ancient Arcadia. According to Pausanias it was founded by Orchomenus, son of Lycaon. In the 2nd century AD, it was not a city anymore, but a village belonging to Megalopolis. It was situated between the rivers Maloetas and Mylaon. It had a temple to Poseidon. The remains of ancient Methydrion have been excavated in 1910.