Telethrio (, ) is a small mountain range in the northwestern part of the island of
Euboea,
Greece. Its maximum elevation is 970 m. It stretches along the west coast of the island, on the
North Euboean Gulf, from
Aidipsos in the west to
Rovies in the east. Its length is about 16 km from east to west. The mountain is forested. There are few villages on the steep southern slope, including Ilia. Villages on the northern slope are Taxiarchis, Kastaniotissa, Galatsades, Kamatriades and Simia.