lay religious group associated with the Japanese Buddhist sect Nichiren-shō-shū. Sōka-gakkai has had rapid growth since the 1950s and is the most successful of the new religious movements that have sprung up in the 20th century in Japan; but in following the teachings of the Buddhist saint Nichiren, it belongs to a tradition dating from the 13th century.

The Sōka-gakkai follows an intensive policy of conversion (shakubuku; literally, “break and subdue”), which increased its membership within a seven-year period (1951–57) from 3,000 to 765,000 families. In the late 20th century the group claimed a membership of more than 6,000,000. Groups paralleling Sōka-gakkai have been started in other countries, including the United States, where the equivalent organization is called Nichiren-shō-shū of America.

Sōka-gakkai conducts educational and cultural activities and publishes extensively. In 1964 it established its own political party, Kōmeitō (Clean Government Party (Kōmeitō, New)), which by the 1980s had become the third largest political party in Japan.

The association was founded in 1930 by Makiguchi Tsunesaburō, a former elementary-school principal, under the name Sōka-kyōiku-gakkai (“Value-Creation Educational Society”). Makiguchi stressed the pragmatic benefit of religion and set as his goal three values: bi (“beauty”), ri (“gain”), and zen (“goodness”). The society suffered from the government's repressive policies toward religious sects during World War II and for a time was disbanded. Makiguchi died in detention during this period. His chief disciple, Toda Jōsei, revived the organization in 1946, renaming it Sōka-gakkai.

In common with other Nichiren movements (see Nichiren Buddhism), Sōka-gakkai places great emphasis on the benefits effected by the chanting of the phrase “Nam Myōhō renge kyō" (“I devote myself to the Lotus Sutra of the Wonderful Law”), which is an invocation of its chief scripture, the Lotus Sutra.