In the antiquity it was named Ikos, later Liadromia or Chiliadromia and in the modern ages, King Othon (in 1838) renamed it Alonissos.

The island belongs to Sporades complex and is the most remote island of the complex. Today it is a relax refuge for people that love nature and tranquility. The southern part of the island is spread with pine forests that stand in sharp contrast to the macchia vegetation, pistacias and arbutuses common in the northern part.

The island is considered the gem of the Aegean due to its wonderful beaches, the landscape and the clean waters along with The National Marine Park of Alonissos which hosts the Mediterranean seal monachus-monachus.