Pythagoreio (Greek: Πυθαγόρειο) is a town and municipal unit on the island of Samos, North Aegean, Greece.

The archaeological remains in the town, known collectively as Pythagoreion, has designated a joint UNESCO World Heritage Site with nearby Heraion.

Ruins of the Byzantine period are visible in the area of Logothetis' Tower on the west side of the harbour.

In the later Ottoman period the centre of the island was Chora, built inland, 4 km northwest of Pythagorio.

During Greek War of Independence the Samian Leader Lykourgos Logothetis built a tower in Pythagorio between 1824 and 1827.

The name of new settlement was originally Tigani, a corruption to the Italian “Dogana” that means "customs", but in 1955 renamed to Pythagorio after the name of famous ancient Greek Mathematician and Philosopher from Samos Pythagoras.