Written in response to popular demand, The Exercise of the Christian Life (1557) offers the reader numerous prayers, meditations, and general advice to live a more devout life. Its author, Gaspar Loarte (c.1498–1578), was a Spanish Jesuit who was serving as rector of the Jesuit college in Genoa, Italy, while composing this treatise, which grew out of his own sermons and ministries there. As one of the first examples of Jesuit devotional literature, the Exercise represents a window into popular piety of the period, marked by a focus on Christ’s passion and death and including detailed recommendations for combating the devil and his temptations in this earthly life. The Exercise of the Christian Life was a best seller from the very beginning, being reprinted dozens of times in the sixteenth and seventeenth centuries and translated into French, Spanish, German, and English. The present volume represents the first annotated modern translation of the text into English.