Adam Nathaniel Yauch (pronounced /ˈjaʊk/; August 5, 1964 – May 4, 2012) was an American rapper, musician, film director, and human rights activist. He was best known as a founding member of the hip hop group Beastie Boys. He was frequently known by his stage name, MCA, and sometimes worked under the pseudonym Nathanial Hörnblowér.

Yauch founded Oscilloscope Laboratories, an independent film production and distribution company based in New York City. A Buddhist, he was involved in the Tibetan independence movement and organized the Tibetan Freedom Concert.