Sphacteria (Greek: Σφακτηρία - Sfaktiria)^[1] also known as Sphagia (Σφαγία)^[2] is a small island at the entrance to the bay of Pylos in the Peloponnese, Greece. It was the site of three battles:

• the 425 BC Battle of Sphacteria in the Peloponnesian War.^[3]
• the 1825 AD Battle of Sphacteria in the Greek War of Independence from the Ottoman Empire
• the 1827 AD Battle of Navarino, also in the Greek War of Independence

The shipwreck of the Irenes Serenade took place near the island in 1980.