A katana (刀 or かたな) is a Japanese sword characterized by a curved, single-edged blade with a circular or squared guard and long grip to accommodate two hands.

Katana were used by samurai both in the battlefield and for practicing several martial arts, and modern martial artists still use a variety of katana. Martial arts in which training with katana is used include iaijutsu, battōjutsu, iaidō, kenjutsu, kendō, ninjutsu and Tenshin Shōden Katori Shintō-ryū. However, for safety reasons, katana used for martial arts are usually blunt edged, to reduce the risk of injury. Sharp katana are only really used during tameshigiri (blade testing), where a practitioner practices cutting a bamboo or tatami straw post.