Populism is the key political phenomenon of the 21st century. From Trump to Brexit, from Chávez to Podemos, the term has been used to describe leaders, parties and movements across the globe who disrupt the status quo and speak in the name of 'the people' against 'the elite'. Yet the term remains something of a puzzle: poorly understood, vaguely defined and, more often than not, used as a term of abuse. In this concise and engaging book, leading expert Benjamin Moffitt cuts through this confusion. Offering the first accessible introduction to populism as a core concept in political theory, he maps the different schools of thought on how to understand populism and explores how populism relates to some of the most important concepts at the heart of political debate today. He asks: what has populism got to do with nationalism and nativism? How does it intersect with socialism? Is it compatible with liberalism? And in the end, is populism a good or bad thing for democracy? This book is essential reading for anyone - from students and scholars to general readers alike - seeking to make sense of one the most important and controversial issues in the contemporary political landscape.