There isn’t a single person who designed the katana prototype; it evolved over centuries through Japanese swordsmithing. The earliest credited figure often mentioned is Amakuni Yasutsuna, who is traditionally said to have forged the first curved Japanese sword, the ancestor of the katana.

Quick context

The katana developed from earlier straight blades influenced by Chinese swords, then shifted into curved forms better suited to mounted combat. That long refinement is why historians usually describe it as an evolution rather than one inventor’s design.

Simple answer

  • Closest traditional answer: Amakuni Yasutsuna.
  • Historical reality: multiple generations of swordsmiths shaped the prototype over time.
  • Earliest foundation: imported Chinese-style straight swords helped inspire the starting point.

If you meant the Suzuki Katana motorcycle instead of the sword, its concept was created by Hans Muth and the Target Design team.