Research and theorizing on gender and age differences in self-esteem have played a prominent role in psychology over the past 20 years. However, virtually all empirical research has been undertaken in the United States or other Western industrialized countries, providing a narrow empirical base from which to draw conclusions and develop theory. To broaden the empirical base, the present research uses a large Internet sample (N = 985,937) to provide the first large-scale systematic cross-cultural examination of gender and age differences in self-esteem. Across 48 nations, and consistent with previous research, we found age-related increases in self-esteem from late adolescence to middle adulthood and significant gender gaps, with males consistently reporting higher self-esteem than females. Despite these broad cross-cultural similarities, the cultures differed significantly in the magnitude of gender, age, and Gender × Age effects on self-esteem. These differences were associated with cultural differences in socioeconomic, sociodemographic, gender-equality, and cultural value indicators. Discussion focuses on the theoretical implications of cross-cultural research on self-esteem.