Alaria (Phaeophyceae, Alariaceae) is a common genus of kelps in the northern hemisphere. Fourteen species are currently recognised of which three (Alaria esculenta (L.) Greville, Alaria pylaii (Bory de Saint-Vincent) Greville, and Alaria grandifolia J. Agardh) are reported for the cold -temperate North Atlantic Ocean. Alaria esculenta, the type species described originally from the North Atlantic, exhibits a range of biogeographically correlated morphotypes suggesting the possibility of multiple specific or intraspecific entities or hybrids (Kraan pers. comm.; Kraan & Guiry 2000 in press). A key to the species of the genus Alaria is given by Widdowson (1971).