Institutes of the Christian Religion (Latin: Institutio Christianae Religionis) is John Calvin's seminal work of systematic theology. Regarded as one of the most influential works of Protestant theology, it was published in Latin in 1536 (at the same time as Henry VIII of England's Dissolution of the Monasteries) and in his native French language in 1541, with the definitive editions appearing in 1559 (Latin) and in 1560 (French).

The book was written as an introductory textbook on the Protestant creed for those with some previous knowledge of theology and covered a broad range of theological topics from the doctrines of church and sacraments to justification by faith alone and Christian liberty. It vigorously attacked the teachings of those Calvin considered unorthodox, particularly Roman Catholicism, to which Calvin says he had been "strongly devoted" before his conversion to Protestantism.