An artificial island is an island that has been constructed by humans rather than formed by natural means. They are created by expanding existing islets, construction on existing reefs, or amalgamating several natural islets into a bigger island.
Early artificial islands can be floating structures in still waters, or wooden or megalithic structures erected in shallow waters (e.g., crannógs and Nan Madol discussed below). In modern times artificial islands are usually formed by land reclamation, but some are formed by the incidental isolation of an existing piece of land during canal construction (e.g. Donauinsel and Dithmarschen), or flooding of valleys resulting in the tops of former knolls getting isolated by water (e.g. Barro Colorado Island).
Some recent developments have been made more in the manner of oil platforms (e.g., Sealand and Republic of Rose Island).
Artificial islands may vary widely in scale, from small islets reclaimed solely for supporting a single pillar of a building or structure, to those which support entire communities.
