This paper explores the sacred feminine embodied in the figure of Avalokiteśvara Bodhisattva (Quán Thế Âm Bồ Tát) within the broader context of the localization of Buddhism in Vietnam. Originating as a male bodhisattva symbolizing compassion in the Mahāyāna tradition, Avalokiteśvara underwent a significant transformation through cultural transmission across Asia. In Vietnam, the Avalokiteśvara Bodhisattva has been reimagined as a maternal, merciful goddess - “Mother Quan Âm”- deeply integrated into local devotional practices and popular spirituality. The study highlights the dynamic interplay between Buddhist metaphysics and Vietnamese indigenous religiosity, particularly in how the feminine aspect of Avalokiteśvara was accentuated to resonate with pre-existing mother goddess worship and matrilineal cultural values. Drawing on interdisciplinary approaches from religious studies, gender studies, and cultural anthropology, the paper argues that this syncretic process not only facilitated the indigenization of Buddhism but also elevated the sacred feminine to a central position in Vietnamese Buddhist cosmology.