In standard English usage the term Septuagint typically denotes the earliest Greek version of the Old Testament. Despite this seeming clarity, it is in fact a fuzzy concept, insofar as the boundaries of its application shift significantly from one context to another. This chapter delineates the four principal ways in which the term is currently used by biblical scholars, and discusses the historical background of each with reference to the reception of the Jewish Greek Scriptures. It begins with their inception in Hellenistic Judaism, and traces their reconfiguration by early Jewish and Christian tradents through to the advent of modernity and the rise of critical scholarship. Current issues in the field of Septuagint Studies are addressed.