Randall Christoph Herman Lesaffer (born 25 April 1968) is a Belgian historian of international law.
In 1998, he obtained his PhD in law from the Leuven on a study on early-modern and Cold War peace and alliance treaties.
He is currently involved, with writing a political history of international law at the end of the Cold War.
He is among others author of European Legal History: A Political and Cultural Perspective by Cambridge University Press.
Lesaffer has published extensively in the field of the history of international law, particularly in early-modern Europe.