The Hours of Catherine of Cleves (Morgan Library and Museum, now divided in two parts, M. 917 and M. 945, the latter sometimes called the Guennol Hours or, less commonly, the Arenberg Hours) is an ornately illustrated manuscript, produced by the anonymous Dutch artist the Master of Catherine of Cleves in c. 1440 in the Gothic art style. It is one of the most lavishly illuminated manuscripts to survive from the 15th century and has been described as the zenith of Northern European illumination. This Book of Hours contains the usual offices, prayers and litanies in Latin, along with supplemental texts, decorated with 157 colorful and gilded illuminations. Today, both parts of the manuscript that forms this book are housed at the Morgan Library and Museum in New York City, U.S.