Unstan (or Onstan, or Onston) is a Neolithic chambered cairn located on Mainland, Orkney, Scotland. The tomb was built on a promontory that extends into the Loch of Stenness near the settlement of Howe and the town of Stromness. Unstan is notable as an atypical hybrid of the two main types of chambered cairn found on Orkney, and as the location of the first discovery of a type of pottery that now bears the name of the tomb.
The site is in the care of Historic Scotland.
The tomb is a particularly well preserved, and somewhat unusual, example of an Orkney–Cromarty chambered cairn. Tombs of this type are often referred to as "stalled" cairns due to their distinctive internal structure. Sources