Agiasos () is a small town and a former municipality on the island of Lesbos, North Aegean, Greece. Since the 2019 local government reform, it became a municipality unit that is part of the municipality Mytilene. The municipal unit has an area of 79.924 km<sup>2</sup>. It is located at the slopes of mount Olympos, at a height of , from Mytilene.