Proposing Chaucer as the inventor of modern tragedy, this work argues that he defined it and produced a memorable example of it in "Troilus and Criseyde"; that his lead was followed by later authors; and that it was his notion of tragedy, rather than any classical or neo-Aristotelian ideas, that was dominant in the age of Shakespeare. The author takes issue with several critical stereotypes about tragedy in the Middle Ages, and contends that it was not a common term and that there was no uniform meaning given to it by the few authors - including Boccaccio - who used the word or wrote what they called tragedies. Chaucer"s approach to tragedy is set in context by contrasting modern with medieval theoretical approaches to the study of genres, and then by analyzing Chaucer"s work, including the tragedies of the Monk"s tale, but mostly "Troilus and Criseyde". Lydgate and Henryson are shown adopting and modifying Chaucer"s theory and practice of tragedy, and its influence is further studied in works of the 16th century.