The small-format prayer book (14.2 x 11.5 x 3.7 cm) was in the personal possession of Charles the Bald (823-877), the grandson of emperor Charlemagne, who became king of Western Francia in 843 and was crowned emperor in Rome in 875. The 46 parchment folios of this manuscript (13.5 x 11 cm) were elaborately decorated in the style of the so-called 'Court School of Charles the Bald' between A.D. 846 and 869. The book contains penitential prayers and the Liturgy of the Hours, Psalms as well as prayers for various occasions, which were modified for Charles' personal use. The entire text is written in gold ink, partially on purple-dyed vellum. The pages are framed by ornamental borders and decorated with elaborate initials. On a double page preceding the prayer for the veneration of the Holy Cross (fol. 38v-39r) the only parts of the illumination containing figural elements are two full-page miniatures showing Charles in adoration of the crucified Christ. The Prayer Book of Charles the Bald, preserved in the treasury of the Munich Residence (ResMü.Schk0004-WL), is the oldest surviving royal prayer book of the Middle Ages. It belongs to a group of magnificent manuscripts commissioned by Charles the Bald which represents the final apogee of Carolingian book illumination. From the 14th century until the Reformation, the manuscript was preserved in the Grossmünster in Zurich. Later it reached monastery of Rheinau (Switzerland), where Duke Wilhelm V of Bavaria was able to acquire it in 1583. The present binding, made of leather with golden embroidery and Bavarian pearls, was probably commissioned by Elector Maximilian I of Bavaria after 1635. It replaced the original book cover (not identified) which, according to historical descriptions, consisted of two ivory reliefs depicting the Annunciation and the Visitation or the birth of Jesus Christ respectively.