Sir Henry Spelman, a founding member of the Society of Antiquaries of London who may be considered the doyen of English antiquaries, made a substantial contribution through his many publications, particularly his Glossarium of 1626, his Concilia of 1639 and, together with his son John, the Psalterium Latino-Saxonicum of 1640. He pioneered the methodical study of historical documents, compiling a guide to the abbreviations and contractions found in medieval manuscripts, and, because some of the documents are in Old English, he made a plan to prepare an Anglo-Saxon grammar and established a lectureship in Anglo-Saxon at the University of Cambridge. After his death his books and papers were dispersed in stages, many of them being bought by subsequent antiquaries. The printed part of this paper surveys the history of his books and papers, with particular attention to his letters, which have never been listed or presented in an organized form despite calls for this to be done since 1930. The supplementary part (online) offers a conspectus of the letters in chronological order with indications of where they are found and of their more important contents. They throw considerable light on how he worked and on his relationship with those who helped him. Themes running through the letters include Spelman’s publications and the preparations for them, the Glossarium, the Concilia and the Anglo-Saxon Psalterium, the reading and transcription of Anglo-Saxon manuscripts, the preparation of an Anglo-Saxon grammar and dictionary and various scholarly enquiries.