Resumo. This article explores the religious dimensions of Confucianism during the Ly-Tran dynasties (1009-1400 AD) in Vietnam, a period marked by significant sociopolitical and cultural transitions. Initially introduced as a moral and ethical philosophy from China, Confucianism underwent a complex process of localization, blending with indigenous Vietnamese beliefs and practices as well as Buddhism and Taoism. Through historical records, literary works, and ritual practices documented in “The Complete Annals of Đại Việt” and other classical texts, this study delves into how Confucianism not only served as a guiding principle for governance, education, and social norms but also manifested religious aspects that influenced spiritual and religious life in Vietnam. The religious aspects of Confucianism during this era are evident in several key areas. Firstly, the concept of Heaven (Tian) and the Mandate of Heaven played a crucial role in legitimizing royal authority, with rulers and Confucian scholars frequently invoking divine will to justify political actions and social order. This sacralization of monarchy underpinned by Confucian ideals facilitated the integration of Confucianism into Vietnamese spiritual life. Secondly, the incorporation of Confucian rituals and practices, such as the Heaven Worship Ceremony (Tế Giao) and the veneration of Confucius and other sages at the Temple of Literature, highlights the religious dimensions of Confucian practice, emphasizing reverence, filial piety, and the moral obligations of rulers and subjects alike. Moreover, the article discusses how Confucianism interacted with and was influenced by Buddhism and Taoism, leading to a syncretic religious landscape in Vietnam. This interaction is illustrated through the blending of Confucian principles with Buddhist and Taoist ideals, affecting notions of kingship, governance, and the cosmological order. In conclusion, the religious aspect of Confucianism during the Ly-Tran dynasties significantly contributed to the shaping of Vietnamese identity, governance, and cultural heritage. By examining the religious dimensions of Confucianism, this article provides a more nuanced understanding of its role in Vietnamese society, highlighting the complex interplay between philosophy, religion, and politics in historical Vietnam.