Linum perenne (Perennial Flax or Blue flax), is a flowering plant in the family Linaceae, native to Europe, primarily in the Alps, but also locally in England. It is a slender herbaceous perennial plant growing to 60 cm tall, with spirally arranged narrow lanceolate leaves 1-2.5 cm long. The flowers are pale blue, 2-2.5 cm diameter, with five petals. The English populations are sometimes distinguished as Linum perenne subsp. anglicum, and high altitude populations in the Alps as Linum perenne subsp. alpinum. The similar western North American species Linum lewisii is sometimes treated as a subspecies of L. perenne.