The range of dietary macronutrient proportions that we observed among brown bear populations supports the nutritional generalism hypothesis that the species has a wide fundamental macronutrient niche. In combination with previous studies documenting the types and compositions of foods consumed by this species, the brown bear can thus be classified as generalist in all three aspects of the multidimensional nutritional niche. Across populations, the geometric mean annual diet of brown bears was close to an equal one‐third proportion (i.e., the simplex barycentre) for all macronutrients despite considerable interpopulation variance, suggesting that the species has a remarkable ability to tolerate the macronutritional characteristics of their nutritional environment. Thus, we provide evidence that one function of omnivory in brown bear is to enable occupation of a diverse range of habitats and macronutritional environments.