Gender and Adolescence: Global Evidence (GAGE) is a nine-year mixed methods longitudinal research and evaluation program. It aims to generate and share evidence on good-practice programs and policies to help adolescent girls in the Global South reach their full potential. GAGE aims to understand what programs and at what points in the second decade of life are most effective in transforming adolescent girls’ lives. The program will generate unique cross-country data that will contribute to global understanding on the impact of existing programs. Its findings will also contribute to a broader understanding of what is needed to reach the ambitious targets of Sustainable Development Goal 5 focused on the empowerment of women and girls globally.