The concept of collective government in the Middle Ages is associated primarily with urban contexts, while lords are usually understood as exercising sole power over their individual rural domains. However, co-lordship, where several lords shared this ownership and authority, was in fact a regular occurrence in much of western Europe. This project seeks to explain the social purpose of co-lordship by understanding how it, too, functioned as a form of corporative government. I will use qualitative and quantitative analyses of administrative records to compare the frequency and forms of lordly collaboration in four regions of France, long considered the exemplar of aristocratic power structures. Each region had different legal, social, and political conditions which could affect co-lordship patterns; identifying the conditions which were most favorable to co-lordship sheds light on the interests vested in power-sharing. The working hypothesis is that co-lordship satisfied demands for greater access to power by multiple individuals at once, but that the cooperation of these lords was essential for the long-term stability and success of the practice. Challenging the dichotomy between solo and corporative government in this way brings lordship in line with the standards of joint authority increasingly observed elsewhere in medieval society, in monarchies and families as well as in towns, and therefore offers essential new social context for understanding these wider trends.