Rǫgnvaldr Óláfsson (fl. 1164) was a twelfth-century King of the Isles. He was a son of Óláfr Guðrøðarson, King of the Isles and a member of the Crovan dynasty. In the 1153, Óláfr was assassinated by three nephews, before his son, Guðrøðr, was able to overcome them and succeed his father as king. By 1158, Guðrøðr was forced from power by his brother-in-law, Somairle mac Gilla Brigte, who was married to Óláfr's daughter Ragnhildr. In 1164, when Somairle was killed in an invasion of Scotland, and while Guðrøðr was away in exile overseas, Rǫgnvaldr briefly seized the kingship for himself, before being overcome by Guðrøðr, who had him blinded and mutilated.