[ABSTRACT:] Religion is a preeminent social institution that meaningfully shapes cultures. Prevailing theory suggests that it is primarily a benevolent force in business, and differences across world religions preclude examining effects that thread across religions.We develop a theoretical account that fundamentally challenges these assumptions by explaininghow and why religiosity—regardless of which religion is prominent—differentiates based on gender, widening the gender wage gap. Guided by an integrated review of the religion literature, we specify three dimensions of gender differentiation—social domains, sexuality, and agency—that explain why religiosity widens the gender wage gap. A series of studies tested our theoretical model. Two studies showcased the predictive power of religiosity on the gender wage gap across 140 countries worldwide and the 50 United States via gender-differentiated social domains, sexuality, and agency, explaining 37% of the variance in the wage gap. U.S. longitudinal data indicated that the gender wage gap is narrowing significantly faster in secular states. Moreover, experiments allowed for causal inference, revealing that gender-egalitarian interventions blocked the effect of religiosity on the gender wage gap. Finally, theoretical and empirical accounts converge to suggest that religiosity’s effect on the gender wage gap applies across the major world religions.