Macrocnemus is an extinct genus of archosauromorph reptile known from the Middle Triassic (Late Anisian to Ladinian) of Europe and China. Macrocnemus is a member of the Tanystropheidae family and includes three species. Macrocnemus bassanii, the first species to be named and described, is known from the Besano Formation and adjacent paleontological sites in the Italian and Swiss Alps. Macrocnemus fuyuanensis, on the other hand, is known from the in southern China. A third species, Macrocnemus obristi, is known from the of Switzerland and is characterized by gracile limbs. The name Macrocnemus is Greek for "long tibia".