During ancient times, Alonissos was known by the name Ikos. According to archaeological findings the island was inhabited since Neolithic times. The islands of Sporades were still adjusted to Pelion back then.
In the small island Kokkinonisi or Vrachos were found tools dated from the Middle Paleolithic Age (330.000 – 100.000 BC) and are the most ancient findings of human existence in Aegean Sea!
In Kokkinokastro location are saved the remains of the ancient town Ikos’ walls.
Remains of the Neolithic settlement are located in the cove of Agios Petros as and in the island of Kyra Panagia.
Dolopes are believed to be the first settlers of the island, who had a close relation to Pelasgi.
In 578 BC Alonissos became part of the Athenaeum Coalition.
In 4th BC Alonissos, as the rest of Sporades islands were occupied by Philip of Macedonia. But Athenians wanted the island as well something that caused many conflicts between these two strong forces.
In 146 BC Romans occupied Alonissos.
During the 3rd AC the island was Christianized. The Byzantine monuments and churches with interior decoration reveal times of financial and cultural robustness from the times of the Byzantine Empire. In 1207 Venetians conquered the island.
In 1538 Turkish came to the island. They sacked and ravaged the island and killed people. The island was abandoned for many years.
At the end of the 16th and the beginnings of the 17th century, life returned to the island. Alonissos, along with the rest of Sporades islands, adjusted to Greece in 1830.