In historical studies, prosopography is an investigation of the common characteristics of a historical group, whose individual biographies may be largely untraceable, by means of a collective study of their lives, in multiple career-line analysis. Prosopographical research has the goal of learning about patterns of relationships and activities through the study of collective biography; it collects and analyses statistically relevant quantities of biographical data about a well-defined group of individuals. This makes it a valuable technique for studying many pre-modern societies.
British historian Lawrence Stone (1919–1999) brought the term to general attention in an explanatory article in 1971. The word is drawn from the figure of prosopopeia in classical rhetoric, introduced by Quintilian, in which an absent or imagined person is figured forth—the "face created" as the Greek suggests—in words, as if present.
Stone noted two uses of prosopography as a historians' tool: first, in uncovering deeper interests and connections beneath the superficial rhetoric of politics, in order to examine the structure of the political machine; and second, in analysing the changing roles in society of particular status groups—holders of offices, members of associations—and assessing social mobility through family origins and social connections of recruits to those offices or memberships. "Invented as a tool of political history," Stone observed, "it is now being increasingly employed by the social historians."
A certain mass of data is required for prosopography research. The collection of data underlies the creation of a prosopography and, in contemporary research, this is usually in the form of an electronic database. But, data assembly is not the goal of prosopographical research; rather, the objective is to understand patterns and relationships by analysing the data. A uniform set of criteria needs to be applied to the group in order to achieve meaningful results. And, as with any historical study, understanding the context of the lives studied is essential.
In the words of prosopographer Katharine Keats-Rohan, "prosopography is about what the analysis of the sum of data about many individuals can tell us about the different types of connection between them, and hence about how they operated within and upon the institutions—social, political, legal, economic, intellectual—of their time."
In this sense prosopography is clearly related to, but distinct from, both biography and genealogy. Whilst biography and prosopography overlap, and prosopography is interested in the details of individuals' lives, a prosopography is more than the plural of biography. A prosopography is not just any collection of biographies—the lives must have enough in common for relationships and connections to be uncovered. Genealogy, as practiced by family historians, has as its goal the reconstruction of familial relationships, and as such, well-conducted genealogical research may form the basis of a prosopography, but the goals of prosopographical research are generally wider.