The concept of Self-Transcendent Experience (STE) occupies a distinctive position within the depth-psychology and allied scientific literatures, functioning as an integrative umbrella construct that draws together phenomenologically disparate states — mystical experience, flow, awe, peak experience, mindfulness, and self-transcendent positive emotions — under a shared structural signature: decreased self-salience and increased felt connectedness. Yaden and colleagues (2017) supply the most systematic empirical architecture, proposing two sub-components — annihilational (the dissolution of self-boundaries) and relational (the expansion into unity with others and environment) — and situating STEs along a unitary continuum first articulated by Newberg and d’Aquili. A key theoretical tension pervades the literature: self-loss is simultaneously a marker of psychopathology (depersonalization disorder, certain psychotic states) and a source of profound well-being and prosocial transformation. This ambivalence demands careful differential diagnosis between positive and pathological instances. A further tension concerns etiology — whether STEs represent adaptive group-level functions, individual relational recalibration, or mere evolutionary spandrels. The corpus also registers a spiritual-secular divide: while the term deliberately avoids theological connotation, it necessarily engages classical categories from James, Stace, and the mystical traditions. The convergence of affective neuroscience, transpersonal psychology, and positive psychology around this construct marks it as one of the more generative nodes in contemporary psychological inquiry.