Japan Proletarian Party (日本無産党) was a short-lived leftist political party in early Shōwa period Japan. The Nihon Musantō was founded by Suzuki Mosaburō and (1892–1978) in March 1937, as a political wing of the labor union movement. Katō, its chairman, won a seat in the 1937 general election, but the party failed to create much popular support against the rising forces of militarism and against the rising inflation in the Japanese economy. In December 1937, its members were arrested in the Popular Front Incident, and the party was disbanded.