Introduction: Physical activity (PA) is a beneficial health behaviour, however most adolescents worldwide are physically inactive. Updated information on the prevalence and trends of PA is important to inform national and international authorities and support countries’ public health policies and actions. This study aimed to present the worldwide, regional, and national prevalence of PA participation according to its frequency in adolescents. Methods: This study is based on cross-sectional surveys of adolescents’ populations from several countries and all regions worldwide. The sample comprised 520,533 adolescents (251,788 boys; 268,745 girls), from 105 countries and regions. Results: Most adolescents engaged in PA up to 3 days/week (57.1%; 95% CI: 56.9; 57.2). The prevalence of engaging in PA every day decreases over the age from 28.2% at age of 11–12 years (95% CI: 27.4; 29.0) to 21.2% at age of 16–17 years (95% CI: 20.3; 22.0) among boys; and from 19.4% (95% CI: 18.5; 20.2) to 11.1% (95% CI: 10.1; 12.0) among girls. For boys and girls who engaged in PA 5-6 days/week, the prevalence increases from countries with the lowest human development index to countries with the highest. Cambodia (7.3%, 95% CI: 3.8; 10.8), Philippines (7.7%, 95% CI: 5.6; 9.7), Sudan (8.8%, 95% CI: 4.7; 12.9), Timor-Leste (8.9%, 95% CI: 5.5; 12.3), and Afghanistan (10.1%, 95% CI: 6.1; 14.1) were the countries with the lowest prevalence of sufficient PA. Conclusions: National, regional, and worldwide data on the prevalence of physical activity in adolescents highlights the importance of improving the global levels of PA, especially in girls. Identifying the factors causing the age-related decrease in physical activity levels will permit public health entities to define priority actions and policies against physical inactivity.