Western esotericism, also known as esotericism, esoterism, and sometimes the Western mystery tradition, is a term scholars use to categorise a wide range of loosely related ideas and movements that developed within Western society. These ideas and currents are united since they are largely distinct both from orthodox Judeo-Christian religion and Enlightenment rationalism. Esotericism has pervaded various forms of Western philosophy, mysticism and religion, pseudoscience, art, literature, as well as music—and continues to influence intellectual ideas and popular culture.

The idea of grouping a wide range of Western traditions and philosophies together under the term esotericism developed in Europe during the late seventeenth century. Various academics have debated various definitions of Western esotericism. One view adopts a definition from certain esotericist schools of thought themselves, treating "esotericism" as a perennial hidden inner tradition. A second perspective sees esotericism as a category of movements that embrace an "enchanted" worldview in the face of increasing disenchantment. A third views Western esotericism as encompassing all of Western culture's "rejected knowledge" that is accepted neither by the scientific establishment nor orthodox religious authorities.

The earliest traditions that later analysis labelled as forms of Western esotericism emerged in the Eastern Mediterranean during Late Antiquity, where Hermeticism, Gnosticism, Neopythagoreanism and Neoplatonism developed as schools of thought distinct from what became mainstream Christianity. Renaissance Europe saw increasing interest in many of these older ideas, with various intellectuals combining "pagan" philosophies with the Kabbalah and Christian philosophy, resulting in the emergence of esoteric movements like Christian Kabbalah and Christian theosophy. The seventeenth century saw the development of initiatory societies professing esoteric knowledge such as Rosicrucianism and Freemasonry, while the Age of Enlightenment of the eighteenth century led to the development of new forms of esoteric thought. The nineteenth-century saw the emergence of new trends of esoteric thought now known as occultism. Prominent groups in this century included the Theosophical Society and the Hermetic Order of the Golden Dawn. Also important in this connexion is Martinus Thomsen's "spiritual science". Modern Paganism developed within occultism and includes religious movements such as Wicca. Esoteric ideas permeated the counterculture of the 1960s and later cultural tendencies, which led to the New Age phenomenon in the 1970s.

The idea that these varying movements could be categorised together under the rubric of "Western esotericism" developed in the late eighteenth century, but these esoteric currents were largely ignored as a subject of academic enquiry. The academic study of Western esotericism only emerged in the late twentieth century, pioneered by scholars like Frances Yates and Antoine Faivre. Esoteric ideas have meanwhile also exerted an influence on popular culture, appearing in art, literature, film, and music.