The longest sword in the world is known as the "Ōdachi" or "Nodachi." The terms Ōdachi and Nodachi are used interchangeably, and both refer to an exceptionally long Japanese sword.

The Ōdachi typically had a blade length of around 3 to 4 feet (approximately 90 to 120 centimeters) or even longer. These swords were characterized by their extended reach and were primarily used by samurai warriors during battles or in ceremonial contexts.

Due to their size and weight, Ōdachi swords were typically wielded with two hands. They were used for powerful sweeping strikes, cutting down multiple opponents, or dismounting riders. The long reach of the Ōdachi allowed samurai to maintain distance from their foes and strike from a position of advantage.

The term Ōdachi translates to "big/great sword," reflecting its exceptional length compared to other traditional Japanese swords like the katana or tachi. However, it's worth noting that the Ōdachi is not commonly used in modern martial arts or combat due to its impracticality in close-quarters fighting or the confined spaces of indoor environments. Instead, it has become more of a historical and ceremonial curiosity.