The Mandaean community provides us with unparalleled access to a library of ancient Gnostic scriptures that are part of the living tradition that has sustained this community across the centuries. This book is a critical edition of one of these Gnostic texts: the Mandaean Book of John. It present a newly edited text, beautifully set in a new font developed for this project, and provides the first full translation into English, together with critical commentary. As an exemplar of Mandaean literature, the Book of John allows us not only to increase our knowledge about Gnosticism – and by extension the related religions of Judaism, Christianity, and Islam – but also to observe the relationship between Gnostic texts, rituals, beliefs, and living practices, both historically and in the present day.