Viola epipsila; The Northern Marsh Violet is very similar to the Alpine Marsh Violet (Viola palustris). See for the differences on that page. The northern marsh violoet is only common in the north-eastern district of Iceland. It grows on rather drier grounds than the alpine marsh violet which prefers more boggy environments.
They are all member of the violet family (Violaceae). The Icelandic name of this species is Birkifjóla.