Comedy and humour have intrigued and puzzled philosophers and scholars since time immemorial. What is the difference between tragedy and comedy? What is the essence of comedy? What are the traits that qualify something as humorous? Why do we laugh? At the same time, with the philosophical curiosity came an inveterate suspicion: comedy and humour have been considered lowly genres not worthy of serious study and unbecoming for intellectually superior audiences; comedy can stir up base instincts that are better kept hidden behind the propriety of good manners; comedy can be immoral and malicious and hence is to be condemned. The chapter surveys this tension between scholarly curiosity and haughty condemnation in philosophy, religions, and aesthetic criticism. It presents the three principal theoretical families which have tried to account for the mechanics of humour and laughter: the superiority theories, the release theories, and the incongruity theories, from ancient Greece to the present day. Finally, the specificities of film comedy are considered—what devices make a comedy a film comedy and which techniques of the medium are deployed by film humour—and a summary and discussion are offered of the principal theories within film studies, from Gerard Mast’s to Jerry Palmer’s to Andrew Horton’s.