Toshio Yamaguchi

is a Japanese politician who served as Minister of Labour and as a member of the House of Representatives in the Diet of Japan.

Yamaguchi was first elected to the House of Representatives in the 1967 general election and served ten consecutive terms in the Diet, holding his seat until the 1996 general election. He served as labour minister from 1984 to 1985 in the cabinet of Prime Minister Yasuhiro Nakasone. During his time in the Diet, he frequently appeared in the media and was dubbed the "Ushiwakamaru of politics."

In 1994, Yamaguchi persuaded the heads of Tokyo Kyowa Credit Association and Anzen Credit Bank to arrange illegal loans for companies controlled by Yamaguchi and his family. In 1996, he was found guilty of breach of trust, embezzlement, fraud and perjury, and sentenced to four years in prison. He appealed the verdict to the Tokyo High Court, and told reporters in 2002 that he was considering a return to office in 2004; his appeal was rejected in February 2003.

At the age of 75, Yamaguchi entered the 2016 Tokyo gubernatorial election as a candidate of the . He placed eleventh out of twenty-one candidates.