This thesis is on the theory and practice of comic sexual euphemism in Renaissance France and England. The term ‘comic sexual euphemism’ means the use of non-literal descriptions for sexual topics for the purposes of comedy, similar to an innuendo or double-entendre. Crucially, instances are often more explicit than straightforward literal statement, so fail to be euphemistic. I use ancient, early modern, and modern theory, as well as my own theoretical insights, and apply this to three types of Renaissance text: texts associated with the court from England and France, medical texts from France and their English translation, and theatre from England and France. Primary authors include Baldesar Castiglione, Pierre de Brantôme, Sir John Harington (who translated Ludovico Ariosto into English – Ariosto is also translated into French by Jean Martin), Laurent Joubert, Jacques Ferrand (translated into English by Edmund Chilmead), Thomas Middleton, Ben Jonson, Edward Sharpham, John Marston, and Pierre de Troterel. At the court of both countries a dangerous line was walked between protecting women and gossiping about them, between proving yourself witty regarding sexual material and going too far. In the world of French medicine, where you might expect professional and clinical language, there is instead a trend towards outrageous sexual humour. As at court, if deemed to have exceeded social norms, this could get writers into trouble. The stage was in some ways a safer environment in which to use comic sexual euphemism, as it was expected more in comic drama. This does not, however, lessen how vibrant and multi-faceted such language could be in early modern drama. Interestingly, similar imagery is found across texts and genres. In this period overall there was a tension between the rhetorical rules which forbid the discussion of the sexually obscene and the clear delight writers took in breaking these.