In the past decade, the Middle English romance Richard Coeur de Lion has attracted a great deal of scholarly attention; nevertheless, the studies have not been as abundant as its richness and complexity may merit. There are two reasons for this: first, Karl Brunner's 1913 edition, which has long been out of print, is virtually inaccessible. Second, even when Brunner's edition is available, its critical apparatus and scanty notes - in Gennan- have long been out of date. This thesis provides an edition of Richard Coeur de Lion from the London Thomton Manuscript, which has never been edited before. The edited text is accompanied byside-glosses and a full critical apparatus, which includes an Introduction, Explanatory and Textual Notes, a complete Glossary, Index of Names, and Episode Chart. In addition, eight maps and fifty-four plates illustrate the edition. The Introduction to the edition is divided into five sections. The first of them, 'Manuscripts & Early Printed Editions', describes the manuscripts and the two early sixteenth-century printed editions in which Richard is extant, and then advances the scholarship with regard to the relationship between the manuscripts. The second section, 'Editing Middle English Texts', revises the methods of editing and their theoretical and pragmatic limits; it then focuses on the particular problems of editing Richard Coeur de Lion. The section ends with a brief account of the life and milieu of the scribe and compiler Robert Thomton. The following section, 'Date of Composition', takes issue with two nineteenth- and early twentieth-century assumptions. First, that the Middle English Richard is a translation of a (lost) Anglo-Nonnan romance and second, that there was an 'original' historical text later' contaminated' by fictional additions. The third section, 'Sources', studies the diversity of sources and influences that lie behind the composition of Richard to show the extent to which this romance has to be studied as the product of a poetic process of re- . . utilization and re-creation of sources; this is illustrated by a case study. The final section of the Introduction, 'History versus Fiction', examines the tension - or lack of it - between the historical and the fabulous parts of the romance, contrasting the medieval self- awareness of Richard as a romance with its modem reception. The section ends with a case study that exhibits Richard's textual wealth.