Istiaia is a town and former municipality located on the island of Euboea in Greece. It serves as the seat of the current municipality of Istiaia-Aidipsos, which was established following the 2011 local government reform.
The settlement derives its name from the ancient Greek town of Histiaea, a location referenced in the works of the poet Homer. The municipal unit of Istiaia covers a total area of 181.299 km2.