This dissertation investigates the early formation of Wŏn Buddhism by situating it in the larger socio-cultural and religious contexts of early-twentieth-century Korea, such as the emergence of indigenous new religions and Buddhist reform movements. It analyzes the texts, practices, and belief systems created by this new Buddhist religion by drawing on archival materials, such as diaries, personal essays, daily reports, and other written documents that testify to the actual historical voices of people’s everyday experiences and beliefs. I examine how the new Tonghak movement’s notion of sich’ŏnju (revering God within one’s heart 侍天主), which encouraged egalitarianism in Korean society at the end of the nineteenth century, influenced both Buddhist reform movements and new religious movements. I focus my analysis on the novel concept of the “congregation of a thousand buddhas and a million bodhisattvas” that the founder of Wŏn Buddhism, Pak Chungbin 朴重彬 (1891-1943), articulated. Pak proposes that his Pulpŏp Yŏn’guhoe (The Society for the Study of the Buddhadharma 佛法硏究會), which was later renamed Wŏnbulgyo (Wŏn Buddhism 圓佛教), was a “congregation of a thousand buddhas and a million bodhisattvas.” This reconceptualization of the saṃgha captures a way of reforming Korean Buddhism from commoners’ point of view by demonstrating how all living beings, including both male and female, ordained and lay, young and old, colonized and colonizer, and intellectual and non- intellectual, could become buddhas and bodhisattvas through the practices and teachings of Buddhism. In deploying this concept, Pak and his disciples laid out the fundamental teachings of Buddhism in a way that would be accessible to all classes of people and applicable to their daily lives, and sought to make their community a religious institution for realizing that vision. I argue that the new praxes and belief systems of Wŏn Buddhism developed through the complex interplay between East Asian Buddhist practices, colonial modernity, and contemporary interpretations of the concept of “religion.” The new methods taught in Wŏn Buddhism, such as mindful “bean-counting” meditation (t’aejosa 太調査) and keeping spiritual journals, provided the tools for common people to attain greater agency in their Buddhist religious pursuits. My dissertation presents the stories of how nameless ordinary rural people, both male and female, created new identities for themselves by becoming Buddhist practitioners. I explore how they developed their insights to see the world in a new Buddhist way, how their worldview was shaped by Buddhism, and how they adapted in their own lives the “mind-praxis” that Pak taught within the Wŏn Buddhist community. My dissertation’s detailed accounts of ordinary people’s practice will expand the intellectual horizons of the field of Buddhist Studies to include more of the lived experiences of ordinary Buddhists. In this, my work makes a key contribution to the literature on East Asian new religions and Buddhist reform movements, Korean Buddhism, colonial modernity, and the lived religious experience of everyday people.