Evidence of cross-cultural differences in beauty ideals belies the claim that such ideals are a “natural” part of the human psyche, rather than being reflective of cultural and social practices. In this chapter, I examine evidence of cross-cultural variation in one specific beauty standard, namely, women’s body size ideals. I present evidence of historical variation in what was perceived as the ideal body size across world regions, but also show how these variations have narrowed more recently. In explanation, this chapter will show how both Westernization and socioeconomic development bring sociocultural changes that promote a thin ideal. I examine evidence in favor of both explanations, and conclude by suggestion that feminist theory offers the potential for a unifying perspective to better understand the nature and role of beauty ideals.