How is pan-nationalism different from other forms of nationalism? This book explores the diversity of pan-nationalism in both theory and practice. Drawing on Rogers Brubaker, the book introduces "pan-nationalism" as a category of practice. It shows that pan-nationalism implied transcending political frontiers, intermittently possessed a pejorative subtext, and differed from unmodified "nationalism" partly due to a retroactively applied success/failure criterion. Pan-nationalists always look across political frontiers, but do not always want a single pan-national state. The book explores the diversity of pan-nationalism through case studies and a selection of pan-national movements such as: Habsburg pan-Slavism from both the Slavic and Hungarian perspective, pan-Saxonism in Europe and North America, pan-Ethiopianism and pan-Somalism in the horn of Africa, and pan-Hinduism online. The book will be of interest to students and researchers of politics including comparative politics, various forms of nationalism and history. The chapters in this book were originally published as a special issue of Nationalism and Ethnic Politics.