The Gender Inequality Index is a country-level measure of gender inequality based on women's levels of reproductive health, social and political empowerment, and labor-market representation. In two studies, we tested the validity of the GII-S, a state-level measure of gender inequality in the USA. In Study 1, the GII-S was associated with objective and subjective measures of wellness among women, including life satisfaction, financial well-being, and perceptions of safety. GII-S was not associated with the Gini coefficient, a well-established measure of economic inequality, suggesting that gender and economic disparities represent distinct aspects of social inequality. Study 2 tested the link between GII-S scores and collective action-specifically, participation in the #MeToo movement promoting awareness of sexual harassment and violence against women. Analysis of geo-localized messages on the Twitter social media platform reveals that higher GII-S scores were associated with fewer tweets containing the #MeToo hashtag. Moreover, GII-S was associated with state-level political orientation: the more conservative a state, the higher its level of gender inequality. Results are discussed in terms of possible socio-cognitive processes underpinning the association between gender inequality and sensitivity to violence against women.