Xenoglossy is the illusion of speaking or understanding a language unknown to the performer, presented as a demonstration of extraordinary mental or psychic ability. In mentalism, xenoglossy effects rely on pre-show preparation, linguistic memorization, or clever scripting to create the appearance of fluency in an unlearned language. This phenomenon is distinct from glossolalia (speaking in tongues) and is framed as a display of subconscious recall or supernatural communication.

The concept of xenoglossy is a compelling addition to mentalism performances, where it may be used to simulate spirit communication, past-life regression, or unexplained linguistic knowledge. Xenoglossy techniques include memorizing key phrases, using phonetic cues, or employing accomplices fluent in the target language to create the illusion of responsive conversation. When combined with storytelling and psychological misdirection, xenoglossy captivates audiences by evoking a sense of mystery around the boundaries of human cognition and memory.