Stac Biorach is a sea stack, 73 metres tall, situated in the Sound of Soay between the islands of Hirta and Soay in the St Kilda archipelago of Scotland. It lies west of the 62 metres high Stac Shoaig
Stac Biorach (at left) and Stac Soay
"Landing place on Stac Lii", illustration from Climbing in St Kilda by Norman Heathcote