This article, based on the author’s work for a dictionary of Shakespeare’s informal English, explores first what is meant by informal English and what data might provide the basis for this dictionary. It then reviews the understanding of different varieties of English in Shakespeare’s works. Finally, a passage from Romeo and Juliet provides the starting point for an analysis and review of some of the different types of informal English found in Shakespeare’s writings. It is hoped that the paper will spark greater interest in informal English from a historical viewpoint.