A tachi (太刀) is a traditional Japanese sword with a curved, slender, and elongated blade, typically worn suspended edge-down from the waist by ashi (suspension hangers) attached to a saya (scabbard). The tachi predates the katana and was the primary battlefield sword for samurai during the Heian (794–1185) and Kamakura (1185–1333) periods.

Sugata (姿, Blade Shape)

• The tachi has a pronounced koshi-zori (腰反り, deep curvature near the tang), giving it a graceful arc ideal for mounted combat.
• The blade is generally longer than a katana, averaging 70–80 cm in length.