In his early twenties, the Tibetan monk Sangyé Gyaltsen (1452–1507) left his monastery to become a wandering tantric yogin. As he moved from place to place, seeking enlightenment beyond the bounds of monasticism, his behavior became increasingly erratic. While some were shocked or even angered by his actions, others were drawn to him. Tsangnyön’s followers described his transgressive behaviors as enlightened action, rooted in authoritative Buddhist scripture. Using biographical sources, Stefan Larsson explores Sangyé Gyaltsen’s transformation into the charismatic ‘Madman of Tsang,’ Tsangnyön Heruka. Best known today as the author of the Life of Milarepa, Tsangnyön Heruka was one of the most influential mad yogins of Tibet. His biography brings its reader face-to-face with an unexpected aspect of Buddhist practice that flourished in fifteenth-century Tibet.