Yiguandao / I-Kuan Tao (), meaning the Consistent Way or Persistent Way, is a Chinese salvationist religious sect that emerged in the late 19th century, in Shandong, to become China's most important redemptive society in the 1930s and 1940s, especially during the Japanese invasion. In the 1930s Yiguandao spread rapidly throughout China led by Zhang Tianran, who is the eighteenth patriarch of the Latter Far East Tao Lineage, and Sun Suzhen, the first matriarch of the Lineage.
Yiguandao started off with a few thousand followers in Shandong in the 1930s, but under the Patriarch and Matriarch's leadership and with missionary work the group grew to become the biggest movement in China in the 1940s with millions of followers. In 1949, Yiguandao was proscribed in mainland China as an illegal secret society and heretical cult as part of the greater antireligious campaign that took place. Yiguandao has since flourished in Taiwan, despite decades of persecution by the Kuomintang that officially ended in 1987 with the legalization of Yiguandao and a government apology. Yiguandao is still not able to be officially promoted in the mainland, but there are many members who live and practice there.
According to Dr. Sebastien Billioud, Yiguandao can be viewed as an updated version of the tradition unity of the three teachings of Confucianism, Taoism, and Buddhism. In Yiguandao's case it also incorporated Christianity and Islam becoming a unity of the five teachings.
Yiguandao is characterized by an eschatological and soteriological doctrine, presenting itself as a way to salvation. It also encourages adherents to engage in missionary activity. Yiguandao is the worship of the source of the universal reality personified as the Eternal Venerable Mother, or the Splendid Highest Deity (). The highest deity is the primordial energy of the universe, identified in Yiguandao thought with the Tao in the wuji or "unlimited" state and with fire. The name used in contemporary Yiguandao scriptures is the "Infinite Mother" () and the "lantern of the Mother" ()—a flame representing the Mother—is the central focus of Yiguandao shrines.