Hildasay (Scots: Hildasay; Old Norse: Hildisey) (from the Old Norse masculine name Hildir with ey "island"),[5] also known as Hildisay, is an uninhabited island off the west coast of the Shetland Mainland.

Hildasay has an area of 108 hectares (267 acres), and is 32 metres (105 ft) in elevation at its highest point.

It consists of red-green granite (epidotic syenite) that was quarried for many years.

A long line of skerries and holms lies to the north west.

[6] As of 2020 there was one house on the island, which was temporarily occupied by charity walker Chris Lewis and his dog Jet when movement restrictions were imposed during the COVID-19 pandemic.