This book is an edited and annotated translation of Karl Renner’s seminal Der Kampf der Österreichischen Nationen um den Staat (1902). Its main topics – national diversity within states and its possible accommodation – occupy the minds of academia and wider society today as much as they did in the multinational Habsburg Empire at the beginning of the 20^th century. The central question of this book, i.e. how different nationalities can peacefully – and on equal footing – co-exist within the boundaries of the same state, has not lost its salience over the course of the hundred and twenty-three years since it was written. If anything, it has only grown in importance and urgency across a world where the nation-state remains a prevalent form of political organisation.