This study conducts two meta-analyses to investigate gender differences in depression, focusing on diagnoses and symptoms, across nationally representative samples from over 90 nations. The meta-analyses aim to estimate the magnitude of the gender difference, elucidate developmental patterns, and incorporate theory-driven moderators such as gender equity. The overall odds ratio (OR) for major depression diagnoses is 1.95 (95% CI [1.88, 2.03]), and the standardized mean difference (d) for depression symptoms is 0.27 [0.26, 0.29]. Age is the strongest predictor of the effect size, with the gender difference emerging earlier than previously thought, peaking in adolescence and then stabilizing in adulthood. Cross-national analyses show larger gender differences in nations with greater gender equity for major depression but not for symptoms. The study highlights the importance of addressing the health disparity in depression, particularly in males, and suggests that gender equity may play a role in reducing these disparities.This study conducts two meta-analyses to investigate gender differences in depression, focusing on diagnoses and symptoms, across nationally representative samples from over 90 nations. The meta-analyses aim to estimate the magnitude of the gender difference, elucidate developmental patterns, and incorporate theory-driven moderators such as gender equity. The overall odds ratio (OR) for major depression diagnoses is 1.95 (95% CI [1.88, 2.03]), and the standardized mean difference (d) for depression symptoms is 0.27 [0.26, 0.29]. Age is the strongest predictor of the effect size, with the gender difference emerging earlier than previously thought, peaking in adolescence and then stabilizing in adulthood. Cross-national analyses show larger gender differences in nations with greater gender equity for major depression but not for symptoms. The study highlights the importance of addressing the health disparity in depression, particularly in males, and suggests that gender equity may play a role in reducing these disparities.