The Nath yogis, with their roots in the tantric milieu of medieval North India, are the instigators of haaha yoga. Their ultimate goal is the transmutation of sexual fluids into the elixir of immortality. The masters of this yoga are siddhas, the possessors of siddhis, the occult powers that culminate in deification. Scholars have noticed the importance of the occult and magic among the Naths, but these categories are rarely given appropriate theoretical considerations. The academic study of esotericism, conversely, directly engages the occult but often restricts itself to Western traditions. This study argues that there are advantages in applying the conceptual vocabulary and theoretical conclusions of esoteric studies to the scholarship on tantra and yoga. The model of esotericism is applied to the Nath yogis through a threefold thematic division of the subject matter: their understanding of body and sexuality, speech and rhetoric, and mind and ideology. Yoga is comparable to magic understood as a quest for power, based on the cultivated imagination and the principle of unions. The study concludes by suggesting that esotericism should be seen as a cross-cultural phenomenon.