Hikoshirō Sadamune (相模國住人貞宗 - Sagami kuni junin Sadamune;[1] born 1298 Einin – 1349 in Shōhei[2]) also called Sōshū Sadamune was a swordsmith of the Sōshū school, originally from Gōshū (also known as Ōmi province) whose works are considered some of the finest blades ever created. His works are often compared with those of the other great Koto era (987-1596) swordsmiths including Sōshū Masamune, Toshiro Yoshimitsu, Go Yoshihiro, Bizen Nagamitsu, and Ike Muramasa. He was a son by blood or adoption[3] of Sōshū Masamune considered by many to be the most famous of the Sōshū masters.[4][5]
After leaving Gōshū province to go to what is now Kanagawa Prefecture, Sadamune became a student of Masamune, sometime around the Namboku-chō[5] era. As a mark of his completion of his teacher's training he inherited the mune part of his name Sadamune from Masamune. Sadamune was not one of the Great Juttetsu trained by Masamune, but his works were regarded to be of the same level as his master's.