An odachi is a type of Japanese sword that is known for its exceptional length. It is often referred to as a "great sword" or "field sword" due to its size. The distinguishing feature of an odachi is its elongated blade, which typically measures around 3 to 4 feet in length or even longer. This makes it significantly longer than a standard katana, which has a blade length of around 2 to 3 feet.

The odachi originated in Japan during the Kamakura period (1185-1333) and reached its peak of popularity during the Muromachi period (1336-1573). It was primarily used by samurai warriors on the battlefield, either on foot or from horseback.

Due to its size and weight, the odachi was a challenging weapon to wield and required considerable strength and skill. It was typically used for slashing and cutting strikes against multiple opponents or for disrupting enemy formations.

The use of the odachi gradually diminished over time as battlefield tactics changed, and the focus shifted more towards the versatility and practicality of smaller swords such as the katana.

Today, the odachi is considered a ceremonial or display piece rather than a practical weapon. It holds historical and artistic significance and is admired for its impressive size and craftsmanship.