Blackhammer Chambered Cairn is a Neolithic cairn on Rousay, in Orkney, Scotland. It is a scheduled monument in the care of Historic Environment Scotland.
It is thought to date from around 3000 BC. The structure is a typical stalled cairn, with an interior divided into seven compartments by pairs of upright stone slabs. The cairn has a modern roof, as the cairn originally was only a few feet high. Access is by a hatchway and ladder in the roof, as the original entrance was sealed. There have been finds of bones and pottery in the cairn.