As a social historian, Guy Geltner's main area of interest is people, their interrelations, and the forces and ideas they shape, and which - in turn - shape them. The focus of his archival work is on urban Italy in the thirteenth and fourteenth centuries. His comparative research covers a large section of Europe, as well as non-industrial societies around the world. Geltner is especially fascinated by mechanisms of social control such as punishment, marginalisation and various forms of social and religious ‘othering' (from deformation to cannibalism). Several of these themes converge in his first monograph, The Medieval Prison: A Social History, and a series of publications exploring the rise of imprisonment as a punitive measure. A second area of focus in Geltner's work is the history of monastic life and religious orders, and more specifically the mendicants - orders such as the Dominicans and Franciscans which relied on charity - and how they were perceived in various circles (literary, religious, peasant society). Geltner recently combined his interests in social control and the history of mendicant orders in a study of deviant behaviour amongst monks and the sometimes violent reaction to their political and material success.

Geltner has been a lecturer in Medieval History at University College and in the Faculty of History at Oxford University since 2008. He has a Bachelor's in History (magna cum laude) from Hebrew University in Jerusalem and a Master's in History from Princeton University, where also obtained his doctorate degree. Geltner is the recipient of various research grants, including the Lincoln College (Oxford) Hardie Postdoctoral Fellowship in the Humanities in 2006 and a one-year international doctorate grant from the Social Science Research Council (New York). Furthermore, Geltner was the recipient of a Yad Hanadiv Postdoctoral Fellowship for 2006-2008.