Biruaslum or Bioruaslam is a stack in the Barra Isles of Scotland, to the west of Vatersay. Approximately 2.5 kilometres from the nearest road, it reaches 72 m (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."