The tantō is a sword, but is used as a knife with a single or double edged blade between 15 and 30 cm long. Originally the tantō was designed as an amrour piercing stabbing weapon, but the edge can be used for slashing as well. Some tantō have particularly thick cross-sections for armor-piercing duty, and are called yoroi toshi.

Tantō were mostly carried by samurai. Women sometimes carried a small tantō called a kaiken in their obi primarily for self-defense.