The Killarney shad (Alosa killarnensis), also called the goureen, is a freshwater fish in the family Clupeidae, endemic to a single lake in Ireland, Lough Leane in County Kerry. Research has shown that it is a landlocked subspecies of the anadromous, twait shad (Alosa fallax), arriving in the lake after the Last Glacial Maximum about 10,000 years ago. This fish is at risk from eutrophication and the introduction of alien species of fish to the lake and the International Union for Conservation of Nature has rated it as "critically endangered".