Phantom island

A phantom island is a purported island which was included on maps for a period of time, but was later found not to exist. They usually originate from the reports of early sailors exploring new regions, and are commonly the result of navigational errors, mistaken observations, unverified misinformation, or deliberate fabrication. Some have remained on maps for centuries before being "un-discovered".

Unlike lost lands, which are claimed (or known) to have once existed but to have been swallowed by the sea or otherwise destroyed, a phantom island is one that is claimed to exist contemporaneously, but later found not to have existed in the first place (or found not to be an island, as with the Island of California).