This MenEngage-UNFPA advocacy brief explores the importance of changing social norms related to men’s ideas and behaviors and examines several questions: Can men support gender equality and learn to live gender-equitable lives? Can men transform the ideas and practices they associate with manhood? Can the spheres where men and boys are socialized and often learn inequitable norms – home, school, work, sports, religion, the media, and others – be changed? This brief will consider responses to these questions in three parts. The first part focuses on "Gender Relations, Gendered Social Norms, and Masculinities," which discusses the context of societal gender norms and their impact on behaviors. The second part of the Brief examines how "Building on the Changes that are Already Happening," which outlines the broad shifts in men's attitudes, and the gender equitable policies and programs that are taking hold globally. Lastly, the final section puts forth "Principles and Key Recommendations for Promoting Gender Equitable Norms Among Men and Boys," which highlights underlying principles for work with and successful engagement of men and boys to transform gender norms.