In this article Bernard Ince surveys and critically examines for the first time the bizarre phenomenon known as the ‘Monkey Drama’ in the British theatre. A genre of early origin, pre-dating the age of Darwinism, it is to be found in all areas of entertainment, especially during the nineteenth century when the quintessential characteristics of simian mimicry were established. Commonly juxtaposed with the legitimate drama in afterpieces, ‘man-monkey’ spectacles not only blurred conventional man–beast boundaries, but also challenged prevailing conceptions of theatrical legitimacy. The genre attracted myriad performers of varied origins and specialisms, whose ability to mimic simian characteristics stemmed not only from agility and flexibility, but also from careful study of the ‘monkey tribe’ itself. While some familiar names figure among the roll-call of simian impersonators, many artists are little known. Although difficult to quantify precisely, the genre had reached its zenith before the middle of the nineteenth century, the 1820s through the 1840s being a significant formative period. After mid-century, popularity was maintained, but to a lesser degree, largely through pantomime, only to decline significantly after 1900. In a broader context, the study furnishes new material for current interdisciplinary debates regarding the relationship between performance, evolution and visual culture in the Victorian period. Bernard Ince is an independent theatre historian who has contributed earlier studies of the Victorian and Edwardian theatre to New Theatre Quarterly.