This text, written in Latin in the 12th century, is believed to be the first real travel book of the Middle Ages. The guide describes the pilgrim routes through France and Northern Spain to the shrine of St James at the cathedral of Santiago de Compostela, and it gives details of where a ccomodation, good food and wines were to be found. It also provides descriptions of many buildings and monuments to be encountered along the routes. Moreover, it offers valuable information for the medieval traveller on topography, social customs, and codes of behaviour, as well as on such modern topics as armed robbery and water pollution. "The Pilgrim's Guide" is a work that can be studied and understood at several levels. This is a critical edition of the text based on the earliest of the 12 surviving copies of the "Guide" - that is the Codex Calixtinus in the Archivo de la Catedral at Santiago de Compostela. Here the Latin text has been edited, fully annotated and collated with all other extant manuscripts of the "Guide", and printed side by side with a new translation into English, also with annotations. The study includes discussions of the text, authorship, script and decoration of the "Guide" as well as a catalogue of all the twelve extant manuscripts with bibliographies and illustrations. It is being published in two volumes, the Latin and English text with annotations in one, and the critical apparatus with illustrations in the other.