Biruaslum or Bioruaslam is a stack in the Barra Isles of Scotland, to the west of Vatersay. Approximately 2.5 kilometres (1.6 mi) from the nearest road, it reaches 72 metres (236 ft) in height and there is a ruined prehistoric fort on the southern side. Francis G. Thompson characterizes it as "high and virtually inaccessible"; James Fisher mentions a "fulmar flying up and down its tiny cliff."