Seal Island in the Great Southern region of Western Australia (located at 35°4′31″S 117°58′29″ECoordinates: 35°4′31″S 117°58′29″E) is approximately 8.5 kilometres (5 mi) south-east of Albany and approximately 3 kilometres (2 mi) offshore from Frenchman Bay in King George Sound. It has a total area of 2.8 hectares (7 acres). The island is designated as a nature reserve (Reserve Number 32199).
The island is composed entirely of granite and is only accessible at the western end.
Matthew Flinders landed on Seal Island during the voyage of the Investigator in 1801, searching for items that were reportedly left by Vancouver and leaving behind a bottle containing a parchment with details of their own arrival and departure.