An archipelago (/ˌɑːrkəˈpɛləɡoʊ/ ^ⓘ AR-kə-PEL-ə-goh),^[1] sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands. Archipelagos are sometimes defined by political boundaries. For example, while they are geopolitically divided, the San Juan Islands and Gulf Islands geologically form part of a larger Gulf Archipelago.^[2]

The word archipelago is derived from the Ancient Greek ἄρχι-(arkhi-, "chief") and πέλαγος (pélagos, "sea") through the Italian arcipelago. In antiquity, "Archipelago" (from Medieval Greek *ἀρχιπέλαγος and Latin archipelagus) was the proper name for the Aegean Sea. Later, usage shifted to refer to the Aegean Islands (since the sea has a large number of islands).

Archipelagos may be found isolated in large amounts of water or neighbouring a large land mass. For example, Scotland has more than 700 islands surrounding its mainland, which form an archipelago.

Archipelagos are often volcanic, forming along island arcs generated by subduction zones or hotspots, but may also be the result of erosion, deposition, and land elevation. Depending on their geological origin, islands forming archipelagos can be referred to as oceanic islands, continental fragments, or continental islands.^[3]

Oceanic islands are mainly of volcanic origin, and widely separated from any adjacent continent. The Hawaiian Islands and Galapagos Islands in the Pacific, and Mascarene Islands in the south Indian Ocean are examples.

Continental fragments correspond to land masses that have separated from a continental mass due to tectonic displacement. The Farallon Islands off the coast of California are an example.

Sets of islands formed close to the coast of a continent are considered continental archipelagos when they form part of the same continental shelf, when those islands are above-water extensions of the shelf. The islands of the Inside Passage off the coast of British Columbia and the Canadian Arctic Archipelago are examples.

Artificial archipelagos have been created in various countries for different purposes. Palm Islands and The World Islands off Dubai were or are being created for leisure and tourism purposes.^[4][5] Marker Wadden in the Netherlands is being built as a conservation area for birds and other wildlife.^[6]

The largest archipelago in the world by number of islands is the Archipelago Sea, which is part of Finland. There are approximately 40,000 islands, mostly uninhabited. ^[7]

The largest archipelagic state in the world by area, and by population, is Indonesia.^[8]

• List of landforms
• List of archipelagos by number of islands
• List of archipelagos
• Archipelagic state
• List of islands
• Aquapelago

• Chisholm, Hugh, ed. (1911). "Archipelago" . Encyclopædia Britannica (11th ed.). Cambridge University Press.
• 30 Most Incredible Island Archipelagos