Gender bias is a social preference for, and positive behavior toward, people of one gender over another. Gender bias can appear as subtle or obvious, conscious or unconscious. It is visible in individual actions, thoughts, and beliefs, but not limited to the individual. Gender bias must be understood as embedded in social life and institutions, such as the family, workplaces, schools, and political institutions. This entry provides an overview of gender bias, with a particular focus on how it materializes in economic, educational, and political institutions and changes over time.