Stomio (Greek: Στόμιο , Greek pronunciation: ['stomio]) is a village and a community of the Agia municipality. Before the 2011 local government reform it was the seat of the municipality of Evrymenes. The 2011 census recorded 553 inhabitants in the village. The community of Stomio covers an area of 37.985 km2.
The ancient city Eurymenae (also Erymnae) was situated near present Stomio. The Greek Orthodox Monastery of Saint Demetrius, situated on the mountain slope above Stomio, was founded in the 6th century and rebuilt in its present form in the 12th century by Byzantine emperorAlexios I Komnenos. Before 1927 Stomio was named Tsagezi (Greek: Τσάγεζι), deriving from the Turkish Çay ağzı which translates to "river mouth". (Çay = river, ağız = mouth, ağzı = the mouth).