This book introduces readers to the widespread phenomenon of how social media platforms such as YouTube, Twitter, and TikTok become an extension of long-standing aspects of musical theatre engagement. Although casual observers may dismiss social media's import, social media has revolutionized the field of musical theatre since the early days of Web 2.0 with spaces such as AOL, LiveJournal, and Myspace. Now, as social media continues to grow in relevance, the nuanced ways in which digital platforms influence musical culture remain ripe for study. Social Media in Musical Theatre moves beyond viewing social media merely as a passing fad or a space free from critical engagement. Rather, this volume takes a serious look at the critical role social media play in musicals, thus challenging how social media users and musical theatre-makers alike approach digital spaces. This book introduces the relationship between musical theatre and social media in the 21st century as well as methods to study social media's influence on musicals through three in-depth case studies organized around marketing on YouTube, fan engagement on Twitter, and new musical development on TikTok.