The monk Chōgen 重源 (1121-1206) is most famous for the rebuilding of Tōdaiji 東大寺. Less understood is the interest Chōgen developed in Chinese Buddhist relic worship during three trips to southern China. Worship of the cremated remains of the Buddha’s body, treated as corporeal relics, had been popular in Japan for centuries by the time of Chōgen, but he was particularly impressed with the form of relic worship he encountered at Ayuwangshan 阿育王山, a mountain temple complex near the Chinese port city of Ningbo. During the Heian Period (794-1185) in Japan, relics were inaccessible to the public, and used almost exclusively for rituals designed to bring benefits to the secular elite. At Ayuwangshan, in contrast, Chōgen witnessed throngs of common, lay devotees prostrating in a slow ascent to the mountain temple, where they could worship the temples’ relic in person. This article examines how Chōgen’s experiences at Ayuwangshan motivated him to fashion mobile reliquaries that could be installed at provincial temples he built across Japan in order to popularize relic worship among common devotees, a novel development in Japanese Buddhist practice.