Nordic theory (or Nordicism) was a theory of racial supremacy prevalent in the late 19th and early 20th century, which claimed that North European peoples constitute a “master race” because of their innate racial capacity for leadership. Nordic theory was influential in Western Europe and North America during the early 20th century and was a major influence on Nazi ideology.The theory drew on the dominant anthropological model of racial categories prevalent in the early 20th century, according to which Europeans were divided into three main sub-categories of the Caucasian race: the Nordic, Alpine and Mediterranean races.

The Nordic race was thought to be prevalent in northern Europe, especially, but not exclusively, among speakers of the Germanic languages, and was characterized by tall stature, wide shoulders, long head- and facial form, straight and fine blond, red, or light brown hair, and blue, grey or green eyes. The Alpine race was thought to predominate in central Europe, and was said to be characterized by short stature, dark hair, dark eyes, narrower shoulders and comparatively round head. The Mediterranean race was thought to be prevalent in southern Europe, Middle East and North Africa, and was said to be characterised by dark hair, dark eyes, narrower shoulders, swarthy complexion, moderate-to-short stature, and moderate of skull.