The title of the greatest Japanese swordsman of all time is a matter of subjective opinion and can vary depending on different criteria and perspectives. However, there are several notable samurai warriors and swordsmen in Japanese history who are widely recognized for their exceptional skill and prowess with the sword. Here are a few renowned figures:

1. Miyamoto Musashi (1584-1645): Miyamoto Musashi is often considered one of the greatest swordsmen in Japanese history. He was a renowned swordsman, strategist, and author of "The Book of Five Rings." Musashi is known for his unorthodox fighting style, mastery of the dual-wielding technique, and undefeated record in over 60 duels.
2. Sasaki Kojiro (1585-1612): Sasaki Kojiro was a highly skilled swordsman and rival of Miyamoto Musashi. He is known for his distinctive longsword technique and was famed for his exceptional speed and reach. The legendary duel between Musashi and Kojiro on Ganryujima is often referenced in Japanese swordsmanship lore.
3. Tsukahara Bokuden (1489-1571): Tsukahara Bokuden was a renowned swordsman and a master of the Kashima Shinto-ryu school of swordsmanship. He is remembered for his numerous duels, military exploits, and teachings on the moral and ethical aspects of swordsmanship.
4. Ito Ittosai Kagehisa (1560-1653): Ito Ittosai Kagehisa was a legendary swordsman and founder of the Itto-ryu school of swordsmanship. He is known for his innovative techniques, teachings, and his influence on the development of swordsmanship in Japan.
5. Yagyu Munenori (1571-1646): Yagyu Munenori was a prominent samurai of the Yagyu clan and a master swordsman. He served as a swordsmanship instructor to the Tokugawa shogunate and was known for his deep understanding of strategy, philosophy, and the practical application of swordsmanship.

These are just a few notable figures, and there are many other highly skilled swordsmen in Japanese history who have left their mark on the art of swordsmanship. The title of the greatest Japanese swordsman is subjective and open to interpretation, as it depends on individual perspectives, criteria, and historical context.