This is the first full study of the important medieval stained glass of Merton College, Oxford. The scheme in the chapel is exceptionally well preserved; with the nave of York Minster, it represents the largest surviving set of early fourteenth-century windows in Britain. Research for this volume in the rich college archives has provided a new date for them, and identified the glazier, whose business is considered locally. Outstanding early fifteenth-century panels from the transepts are attributed to the workshop of Thomas Glazier, who had worked for William of Wykeham, Chancellor of England. Seven windows in the Old Library contain the earliest glazing to survive from any English library. The glass will therefore be of interest to many students of English medieval art and architecture. A general introduction also explores the potential of the monument for study within a university context. Merton was a model for the self-governing graduate college of the later middle ages in England. The glass invites consideration of the relationship between art and ideas, in a lost astrological window, for example; and the self-presentation of the scholar and college communities, both to themselves and to the society that supported them. As a result of the central place of the universities in national life, the Merton glass was an inspiration during the Gothic revival to artists and glazing businesses such as the Pre-Raphaelite John Everett Millais, and Morris, Marshall, Faulkner & Co. The medieval glass is catalogued, fully illustrated and supported with restoration diagrams. There are forty colour plates. The post-medieval glass is also catalogued.