This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book approaches blasphemy as a breach of religious prohibitions – a trans-historical and transcultural phenomenon that changes over time. It consists of case studies that cover the main religious traditions. The book reflects on blasphemy in a secular context and explores how hate-speech laws sacralise the inner feelings of individuals and can be seen as a secular version of blasphemy. It traces the development of blasphemy legislation in medieval Europe, and argues that medieval Christians’ accusations of blasphemy were mostly theological and legal constructs. The book analyses the configurations of belief, critique and religious freedom in Russia in the wake of the 2012 Pussy Riot performance. It argues that this “punk-prayer” revealed a “power-disturbing” potential as conservative Orthodox groups have started to challenge the authority of the state and the church leadership.