Over the past several decades, there has been a sharp increase in obesity across all population groups in the United States. In fact, the United States has one of the highest rates of obesity compared to other countries throughout the world. Obesity has become a national public health concern because it is related to a number of negative health, social, psychological, and economic outcomes. It is particularly concerning because racial/ethnic minorities and populations with the least education and highest poverty rates bear the largest burden of obesity. In addition, disparities in obesity tend to be gendered, with women experiencing the largest disparities in obesity by income, education, and race/ethnicity. In this review, I describe how social inequality is linked to obesity in the United States. I highlight elements of disadvantage at the individual-, family-, school-, and neighborhood-level that are linked to energy intake and expenditure, which are directly related to obesity, and draw from evidence and theories from multiple fields of the social and medical sciences. I also highlight the important role stress may play in linking disadvantage to obesity, particularly for women. I argue that understanding the complex mechanisms and processes that link social inequality to obesity requires multidisciplinary and multilevel frameworks.