Dasho Keiji Nishioka (Japanese: 西岡 京治, Nishioka Keiji; 14 February 1933 – 21 March 1992) was a Japanese botanist. He was dispatched to the Kingdom of Bhutan by the Japanese Government to help modernise the Bhutanese agricultural sector. Nishioka worked in Bhutan as an agriculture expert for 28 years, from 1964 till his death in 1992. Nishioka's work helped improve the cultivation of rice and vegetables in Bhutan's Paro and Zhemgang dzongkhags (districts). He also participated in civic infrastructure development efforts in Zhemgang.