Ryuichi Doi

was a Japanese politician who served in the House of Representatives in the Diet (national legislature) as a member of the Democratic Party of Japan. He was born in Seoul, when Korea was under Japanese rule. He attended Tokyo Union Theological Seminary, earning a master's degree. In 1990 he was elected for the first time as a member of the Japan Socialist Party.

In April 2014, he was awarded the Order of the Rising Sun, Grand Cordon.

He was an active pastor for the United Church of Christ in Japan, and preached at the Wada Mountains Salt Mission, which was attached to Keiseien (Asago City, Hyōgo Prefecture), a support facility for people with disabilities under the umbrella of a social welfare corporation that he chaired.

He died on 22 January 2016 at a hospital in Kobe, aged 76. He was posthumously awarded the rank of Shoshii.