Dō-maru (胴丸), or "body wrap", was a type of chest armour (dou or dō) worn by the samurai class of feudal Japan. Dō-maru first started to appear in the 11th century as an armour for lesser samurai and retainers. Like the O-yoroi style it became more common in the Genpei War at the end of the 12th century.
There were quite a number of similar styles and types of Japanese armor; the dō-maru is particularly defined by the fact that a dō-maru opens on the right side as opposed to the haramaki style which opened in the back and the ō-yoroi the cuirass of which is completely open on the right side requiring a separate plate (waidate) to cover the right side. The ō-yoroi was a heavy box like armour meant for use on horse back, it was also expensive to make. The dō-maru like the haramaki had more skirt plates (kusazuri) than an ō-yoroi and was lighter, closer fitting and less expensive to make. The dō-maru was easier to fight with on foot and eventually even higher status samurai adopted the dō-maru over the ō-yoroi.
Dō-maru were constructed from small scales of leather or metal laced into plates with cord and lacquered. Then each plate was laced together to form the armor. Due to the weight of iron, armour makers limited its use to the most vital parts of the armor and used leather for the remainder.