This paper investigates the determinants of child marriage using a new data set from rural India. Our model estimates the relative importance of economic factors and social norms in determining the prevalence of child marriage. We find that the probability of a girl becoming a child bride, defined as married before the age of ten, is highly correlated with the prevalence of child marriage within her own caste and village, even after controlling for household and village characteristics. Specifically, if the proportion of child brides within a caste and village were to be reduced by half, the likelihood of a girl being a child bride would be reduced by about 20 percent. Parental literacy, caste, and having electricity in the home are also found to be significant. However, economic factors, including household income and whether income is below the village mean, appear to be much less important determinants of child marriage.