This chapter provides an overview of genre as a tool for analyzing manga. The main genres in manga are based on demographics, shōnen (boys) manga and shōjo (girls) manga. This chapter discusses how shōnen and shōjo manga evolved, along with other related genres: gekiga, seinen manga, boys love (BL), and josei manga. It also discusses as examples two thematic genres that appear in both shōnen and shōjo, sports manga, and isekai (other world). Understanding the parameters and meanings of manga genres explains not only specific narrative and aesthetic choices but also how manga functions socially for readers. Demographic genres inform readers of what types of narratives and aesthetics to expect. Looking at how thematic genres such as sports and isekai change to fit shōnen or shōjo conventions shows how genres are flexible categories continually evolving to reflect readers’ interests.