It is now more than a generation since Gaston Le Hardy published _Le dernier des ducs normands: étude de critique historique sur Robert Courte-Heuse_ (1882), the only monograph upon Robert which has hitherto appeared. In spite of its age, if this were the critical study which its title implies, the present essay need hardly have been undertaken. But it makes no use of documentary materials, and is unfortunately a work of violent _parti pris_, quite lacking in criticism according to modern standards. “J’ ai entrepris,” says the author in his preface, “à l’aide de quelques autres chroniqueurs, une lutte contre notre vieil Orderic Vital, essayant de lui arracher par lambeaux la vérité vraie sur un personnage dont il ne nous a donné que la caricature.” It may be granted that Ordericus Vitalis was a hostile critic, who sometimes did Robert scanty justice; but assuredly there is no occasion for polemics or for an _apologia_ such as Le Hardy has given us, and I have no intention of following in his footsteps. My purpose is a more modest one, namely to set forth a full and true account of the life and character of Robert Curthose upon the basis of an independent and critical examination of all the sources. To any one acquainted with the state of the materials on which the investigator must perforce depend for any study of the late eleventh and early twelfth centuries, it will not be surprising that there are many gaps in our information concerning Robert’s life and many problems which must remain unsolved. I have tried at all times to make my own researches and to draw my own conclusions directly from the sources when the evidence permitted, and to refrain from drawing conclusions when it seemed inadequate. But my indebtedness to the secondary writers who have preceded me in the field is abundantly apparent in the index and in the footnotes, where full acknowledgments are made. The works of E. A. Freeman upon the Norman Conquest and upon the reign of William Rufus have proved especially helpful for Robert’s life as a whole, as have also various more recent monographs which bear upon his career at certain points. Among these are the works of Louis Halphen upon the county of Anjou, of Robert Latouche upon Maine, and of Augustin Fliche upon the reign of Philip I of France. For the chapter on the Crusade much use has been made of the detailed chronology of Heinrich Hagenmeyer and of the exhaustive notes in his well known editions of the sources for the First Crusade, as well as of the admirable monograph by Ferdinand Chalandon upon the reign of the Emperor Alexius I. The appendix _De Iniusta Vexatione Willelmi Episcopi Primi_ has already been published in the _English Historical Review_, and is here reproduced by the kind permission of the editor.