leftist Japanese political party founded in 1922. Initially, the party was outlawed, and it operated clandestinely until the post-World War II Allied occupation command restored freedom of political association in Japan; it was established legally in October 1945.

In 1949 the JCP won 35 seats in the House of Representatives and nearly 10 percent of the vote, but external and internal pressures so shattered the party that it lost all its seats in the elections of 1952. In 1955 the party reorganized and began a steady ascent in membership and seats in the Diet (legislature), which peaked when it won 39 House seats in 1979. In the 1980s the party averaged between 5 and 10 percent of the vote and held on average about 30 seats in the House of Representatives. In 1993 it was reduced to only 15 seats, and in subsequent years it modified its policies to become a more traditional democratic socialist party. It also took a strong stance against nuclear weapons. Though it raised its seats to 26 in 1996, its support eroded in subsequent elections. It has taken an increasingly nationalist stance. In the 1960s the JCP broke with the Soviet and Chinese parties, causing a schism with its more radical members; it restored relations with the Chinese Communist Party in 1998. Its daily paper Akahata (“Red Flag”) has a large national circulation.