The Aegean Sea with its large number of islands

An archipelago (pronounced /ɑrkəˈpɛləgoʊ/) is a chain or group of islands. The word archipelago means "chief sea", from Greek arkhon (arkhi-) ("leader") and pelagos ("sea").

Archipelagos are usually found in the open sea; less commonly, a big landmass may neighbor them, an example being Scotland which has more than 700 islands surrounding the mainland. Many archipelagos are volcanic, forming along mid-ocean ridges or hotspots. Others are island arcs neighboring an oceanic trench. Many other processes create archipelagos, including erosion, deposition, and land elevation.