Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States. Avalonia is named for the Avalon Peninsula in Newfoundland.

The Avalon Peninsula is a large peninsula that makes up the southeast portion of the island of Newfoundland. It is 9,220.61 square kilometres (3,560.10 sq mi) in size.