The Zenkoku Suiheisha (Japanese: 全国水平社, lit. "National Levelers' Association") was a Japanese human rights organization founded on 3 March 1922 to advocate for the liberation of the Burakumin, an outcast group subjected to discrimination. Launched in Kyoto in the liberal atmosphere of the Taishō era, the Suiheisha was the first national organization formed by the Burakumin to protest discrimination. It was preceded by smaller, government-sponsored improvement movements known as Yūwa (conciliation), but the Suiheisha distinguished itself by rejecting government assistance and advocating for self-liberation through direct action protest campaigns known as kyūdan (denunciation).

The movement grew rapidly, establishing a national network and a newspaper, the Suihei Shimbun. Its ideology evolved from a broad human-rights focus to an engagement with leftist political theories, particularly anarchism and Bolshevism. This led to internal factional struggles throughout the 1920s, which, combined with increasing government repression under the Peace Preservation Law, brought the organization to the brink of collapse by the early 1930s.

The Suiheisha was revived in 1933, spurred by a successful national campaign against a discriminatory court ruling and the development of a new, coherent theory of liberation known as Buraku Iinkai Katsudō (Buraku Committee Activity). This strategy linked local, practical demands for improved living conditions with a broader political struggle. However, under the rising tide of militarism and nationalism in the late 1930s, the Suiheisha's leadership gradually abandoned its leftist positions. The organization began cooperating with the government's Yūwa policy and supporting the war effort. It was formally ordered to dissolve in January 1942 and was absorbed into the state-controlled Dōwa Hōkōkai (Dōwa Public Service Group). Despite its dissolution, the Suiheisha's two-decade history of activism and theoretical debate provided a critical foundation for the post-war Buraku Liberation League.

The Burakumin are a Japanese minority group who are descendants of the outcast communities of the Tokugawa period (1603–1868), principally the eta and hinin. Historically, these groups were associated with occupations considered impure in Shinto and Buddhism, such as leatherworking, butchery, and handling the dead. During the Tokugawa period, the government enforced a rigid social hierarchy, formalizing the Burakumin's outcast status through legal restrictions on their dress, residence, and social interactions.

On 28 August 1871, the Meiji government issued the Emancipation Declaration, which legally abolished the titles of eta and hinin and granted the former outcasts the status of "new commoners" (shinheimin). However, the declaration did not include measures to integrate the group into Japanese society or address the deep-seated prejudice against them. Discrimination continued in marriage, employment, and education, and the government's modern family register system made it easy to identify individuals of Burakumin descent, facilitating their exclusion. Stripped of their traditional occupational monopolies and facing social ostracism, most Burakumin lived in impoverished, segregated communities and experienced living conditions far below those of the majority population. By the early 20th century, the Burakumin population was estimated by the government to be around one million, or approximately 1.5% of the total population of Japan.

In the early 20th century, a number of small, local self-improvement movements known as kaizen undō emerged within Buraku communities. Inspired by the liberal ideas of the Meiji era, these groups, often led by wealthier Burakumin, aimed to achieve social acceptance by improving their communities' living standards and moral conduct. One of the most prominent was the Bisaku Heiminkai, founded in Okayama Prefecture in 1902 by Miyoshi Iheiji.

In response to the emergence of these autonomous groups and the perceived threat of socialism, the government initiated its own program, known as the Yūwa ("conciliation" or "harmony") policy. Beginning around 1908, the government encouraged the formation of Yūwa groups, supervised by local officials and police, which aimed to promote patriotism and social harmony while providing limited funding for community improvement projects. These early movements, while doing little to end discrimination, helped to create a network of communication between Buraku communities and fostered a growing consciousness of their shared identity and the injustice they faced.

The social and economic turmoil following World War I created a fertile environment for social activism in Japan. The 1918 rice riots, a series of nationwide violent protests against the rising price of rice, demonstrated the potential for mass discontent, while the Russian Revolution inspired the growth of leftist movements. In the spring of 1919, three young men from a Buraku community in Nara Prefecture—Sakamoto Seiichirō, Saikō Bankichi (pen name of Kiyohara Kazutaka), and Komai Keisaku—formed a discussion group called the Tsubamekai (Swallow Club). Sakamoto and Saikō had been exposed to socialist and anarchist thought while studying in Tokyo and were seeking a means to escape discrimination. A turning point came in July 1921 with the publication of an article by the socialist thinker Sano Manabu. Sano argued that Burakumin liberation could not be achieved through government philanthropy but required an autonomous organization that would fight for its own rights while allying with the broader proletarian movement.