This Companion, the first dedicated to the philosopher and historian Xenophon of Athens, gives readers a sense of why he has held such a prominent place in literary and political culture from antiquity to the present and has been a favourite author of individuals as diverse as Machiavelli, Thomas Jefferson, and Leo Tolstoy. It also sets out the major problems and issues that are at stake in the study of his writings, while simultaneously pointing the way forward to newer methodologies, issues, and questions. Although Xenophon's historical, philosophical, and technical works are usually studied in isolation because they belong to different modern genres, the emphasis here is on themes that cut across his large and varied body of writings. This volume is accessible to students and general readers, including those previously unfamiliar with Xenophon, and will also be of interest to scholars in various fields.