Nakanishi Koseki (1807-1884) was a Japanese painter active from the end of the Edo period to the Meiji period. He was born in Ashiya, Chikuzen Province (Fukuoka Prefecture). His name was Juhei, and later Kotobuki. His family name was Jupei, and later Kotobuki. His aliases include Chikuso and Senoka. He studied painting in Kyoto under Matsumura Kagefumi of the Shijo School, then in Osaka under Shinozaki Kotake, a student of Chinese studies, before returning to Kyoto to study nanga under Oda Kaisen.
He was a pupil of Hine Taizan in the nanga world at the end of the Edo period, and received stipends from the Chikuzen and Tsu clans. After the Meiji Restoration, he became one of Kyoto’s leading nanga artists, and when the Kyoto Prefectural School of Painting was established in 1878, he was appointed to teach at the school. His students included Yoshitsugu Kozan, Ueda Tekko, and Kinugasa Goya, and he is regarded as the father of the Fukuoka nanga school.