In traditional Korea, the king controlled customs, including Buddhist practices, and the fortune of Buddhism also depended on his will. In that context, this paper examines how Korean kings in medieval Korea, which is equivalent to the Koryŏ (高麗, 918–1392) dynasty, understood Buddhism in terms of the Three Jewels of Buddhism—the Buddha, His teaching, and the san˙gha (the monastic community)—focusing on King Hyŏnjong (顯宗, r. 1009–1031) and King Kojong (高宗, r. 1213–1259). They understood Buddhism in terms of Chinese systems of thought such as Confucianism and used it for their secular goals, putting the monastic community under their control. Koryŏ kings' primary duty was to secure the eternity of the royal house. To that end, they took Confucianism as the political ideology and Buddhism as a dominant religious force to support important Confucian concepts of loyalty and filial piety. Buddhist services performed by them had the same goal and Buddhist texts served as objects of worship to invoke blessings. However, the Buddhism that Koryŏ kings understood belonged to the Mahāyāna Buddhist tradition and it was different from early Buddhism. This difference elicits a large body of questions, including the actual nature of Koryŏ Buddhism. These issues remain for in-depth research in the future.