Nishinoumi Kajirō I (西ノ海 嘉治郎, February 19, 1855 – November 30, 1908) was a Japanese professional sumo wrestler from Sendai, Satsuma Province.

[1] He was promoted to the top makuuchi division in 1879, and made sekiwake in September 1879, a tournament which was held under the joint auspices of the Kyoto and Osaka sumo organisations.

[2] Nishinoumi fell to sekiwake in January 1886, despite recording a kachi-koshi winning score, as at the time a sekiwake on the east side of the banzuke with a better record could overtake an ōzeki on the same side.

He produced several top wrestlers from Kagoshima Prefecture, amongst them the 25th yokozuna Nishinoumi Kajirō II (the great-grandfather of current Izutsu head Sakahoko) who succeeded him upon his death from heart failure in 1908.

[1] Key:d=Draw(s) (引分);   h=Hold(s) (預り) Divisions: Makuuchi — Jūryō — Makushita — Sandanme — Jonidan — Jonokuchi *Championships for the best record in a tournament were not recognized or awarded before the 1909 summer tournament and the above unofficial championships are historically conferred.