Blasphemy, understood broadly as transgression against the sacred, can be found in all religious traditions. In some contexts, blasphemous words or images cause outrage, while elsewhere, it is brushed off as irrelevant. Why? This chapter traces the roots of blasphemy as a religious offence and follows its trajectory from Christianity to European secular law. With colonialism, blasphemy was aligned with similar concepts in other religious traditions and became a global phenomenon.