Otto III (980–1002) was one of the most powerful rulers in Europe in the late tenth century. He is also one of the most enigmatic. The son of the German emperor Otto II and the Greek princess Theophanu, he came to the throne at the age of three and was only twenty-one years old at the time of his death. Nonetheless, his reign had a lasting impact on both Germany and Italy for generations. In this book, Gerd Althoff provides a much-needed biography of this fascinating figure. In the process, he uses Otto’s life to explain how in practice early medieval kingship worked.