Mastodon Island is an island in the Secret Archipelago. It is roughly west of Swallow Island. It is named after the Mastodon, whose lair, Speedy, is the hulk of a barge on the south coast of the island. The other major landmark on Mastodon Island is a heronry, whose tall trees are useful in surveying (SW13, SW30).

Community content is available under CC-BY-SA unless otherwise noted.