A translation of a unique 17th-century compendium of samurai heraldry annotated with the symbolism and stories behind the banners. O-umajirushi is the earliest surviving colour compendium of Japanese crests and heraldry. At the time, woodblock printing was just starting to allow for widespread distribution of books in Japan. O-umajirushi took advantage of this technology to make colour reproductions of the various banners and other devices used by 170 different samurai commanders. This translation presents copies of the original pages of O-umajirushi with translations, annotations, explanations, and comparisons, as well as thirty pages of context, background information, and historic images. It provides an in-depth look at samurai heraldry and into a key historical source.