Kūsankū (クーサンクー) or Kōshōkun (公相君) was a Chinese martial artist who is said to have visited Okinawa during the Ryukyu Kingdom in the mid-18th century.^[1] He performed a martial art called kumiai-jutsu (組合術) in Ryukyu, which is believed to have contributed to the later development of karate.

According to "Ōshima Records" (大島筆記, 1762) by Yoshihiro Tobe, on April 26, 1762 (lunar calendar), a ship carrying Ryukyuan envoys set sail for Satsuma (present Kagoshima Prefecture). On the way, however, it was caught in a storm and drifted ashore on Ōshima, a small island in Tosa (present Kochi Prefecture). The crew consisted of 52 people, including Shiohira Pēchin Seisei (潮平親雲上盛成).

The book, "Ōshima Records," is a record of interviews conducted by Tōbe Yoshihiro, a Confucian scholar of the Tosa Domain, with the crew members, and contains a detailed description of the domestic situation in Ryukyū in the mid-18th century, including descriptions of Kūsankū and Kumiai-jutsu (literally, the art of grappling).

The book describes a recent visit to Ryukyu by a Chinese martial arts master named Kōshōkun, who demonstrated a martial art called kumiai-jutsu. The "recent" refers to the year 1756, when the Qing Dynasty's envoy visited Ryukyu, and it is commonly believed that Kōshōkun may have been a military officer on this envoy's mission. Kūsankū is the Okinawan dialect for Kōshōkun.

There is no mention anywhere of a relationship with karate or his teaching of kumiai-jutsu to the people of Ryukyu, but this book has been repeatedly mentioned in connection with karate because it is one of the few references to bare-knuckle martial arts in the Ryukyu Kingdom period.

According to Tobe, "Kōshōkun" is a title in praise of the man and not his real name. Hence, the identity of Kōshōkun is unknown, although various guesses have been made to this day.

The karate kata "Kūsankū" is said to be a kata taught by Kōshōkun, but there are no primary historical documents to prove this, the only evidence is the name of the kata and oral tradition. This kata was passed down from Kusanku's student Tode Sakugawa. Many variations of Kusanku kata exist, however the most unique one is known as "Tachimura no Kusanku" in KishimotoDi, this version was passed on by a student of Kanga Sakugawa known as Bushi Tachimura, a contemporary to the more famous Bushi Matsumura. The kata of KishimotoDi remain unaltered by Anko Itosu.