["Journal of School Health, Volume 96, Issue 8, August 2026. ", "\nABSTRACT\n\nBackground\nThis study examined trends in physical activity among Baltic adolescents across the intersection of gender and socio‐economic status (SES).\n\nMethods\nData were gathered from Health Behavior in School‐aged Children (2001–2018) (n = 61,619). No or low moderate‐to‐vigorous physical activity (MVPA) (≤ 1 day/week of 60 min/day of MVPA), insufficient physical activity (not engaging in 60 min/day of MVPA daily), gender, and SES were self‐reported.\n\nResults\nFrom 2001 to 2018, girls and adolescents with low and medium SES experienced a higher probability of no or low MVPA and insufficient physical activity than boys and adolescents with high SES, respectively. Compared to boys with high SES, the other gender × SES groups were more likely to experience insufficient physical activity, with differences more consistent among girls.\n\nImplications for School Health Policy, Practice, and Equity\nActions to promote physical activity should prioritize school‐aged girls from disadvantaged socio‐economic backgrounds.\n\nConclusions\nPhysical activity is unequally distributed among adolescents, with girls and adolescents with lower SES being more likely to have no or low MVPA and insufficient physical activity in the Baltic States. Notable inequalities in physical activity emerged when the intersection of gender and SES was considered simultaneously, especially for no or low MVPA.\n"]