founder of Muhammadiyah, an Islāmic reform movement with great impact on the practice of Islām in Indonesia and strong influence on many nationalist leaders.

Dachlan was a wealthy merchant who made the pilgrimage to Mecca shortly after 1900. On his return, he became active in religious reform activities, first in formalistic issues of ritual and subsequently on broader substantive issues then being raised by reformers in Egypt. In essence, the reformers sought to abandon the four different schools of interpretation of Islāmic law and return to the precepts of the Qurʾān, hoping thus to generate a body of Islāmic thought suited to a modernizing society. Muhammadiyah, founded in May 1912, followed Western organizational models, and Dachlan won legal recognition for it from the government of the Dutch East Indies. Muhammadiyah's practical program stressed education and social work, including the founding and operation of schools, hospitals, and related activities; it modelled itself on the programs of Christian missionary societies, whose influence Muhammadiyah hoped to reduce. The movement avoided political activity, but Dachlan maintained close connections between his organization and the openly political Sarekat Islām (Islāmic Association).

In 1915 Muhammadiyah's schools were granted a government subsidy and began to attract children of ambitious Indonesians seeking to improve their children's opportunities through education but wishing to do so in a Muslim rather than a Christian context. After 1920, Muhammadiyah spread from its Jogjakarta base to the rest of Java and the outer islands and became one of the most powerful influences on the emerging Indonesian middle class.