This chapter investigates the plurality of agents involved in premodern diplomacy by considering the dialectic between juridico-political doctrines and diplomatic practice. After an initial consideration of the topic’s medieval roots, the article focuses on the literature on the ambassador in early modern times and argues that while their primary focus has always been the fully accredited official ambassador, jurists and political thinkers have inevitably also had to tackle the question of other diplomatic figures, as well as issues raised by the latter’s involvement.