Mediumship is the practice of purportedly mediating communication between familiar spirits or spirits of the dead and living human beings. Practitioners are known as "mediums" or "spirit mediums". There are different types of mediumship or spirit channelling, including séance tables, trance, and ouija.

Belief in psychic ability is widespread despite the absence of objective evidence for its existence. Scientific researchers have attempted to ascertain the validity of claims of mediumship. An experiment undertaken by the British Psychological Society led to the conclusion that the test subjects demonstrated no mediumistic ability.

Mediumship gained popularity during the nineteenth century, when ouija boards were used as a source of entertainment. Investigations during this period revealed widespread fraud—with some practitioners employing techniques used by stage magicians—and the practice began to lose credibility. Fraud is still rife in the medium or psychic industry, with cases of deception and trickery being discovered to this day.

Several different variants of mediumship have been described; arguably the best-known forms involve a spirit purportedly taking control of a medium's voice and using it to relay a message, or where the medium simply "hears" the message and passes it on. Other forms involve materializations of the spirit or the presence of a voice, and telekinetic activity.

The practice is associated with several religious-belief systems such as Shamanism, Vodun, Spiritualism, Spiritism, Candomblé, Voodoo, Umbanda and some New Age groups.