Keith Noel Emerson (2 November 1944 – 11 March 2016) was an English keyboardist, songwriter, composer and record producer. He played keyboards in a number of bands before finding his first commercial success with the Nice in the late 1960s. He became internationally famous for his work with the Nice, which included writing rock arrangements of classical music. After leaving the Nice in 1970, he was a founding member of Emerson, Lake & Palmer (ELP), one of the early progressive rock supergroups.

Emerson, Lake & Palmer were commercially successful through much of the 1970s, becoming one of the best-known progressive rock groups of the era. Emerson wrote and arranged much of ELP's music on albums such as Tarkus (1971) and Brain Salad Surgery (1973), combining his own original compositions with classical or traditional pieces adapted into a rock format. Following ELP's break-up at the end of the 1970s, Emerson pursued a solo career, composed several film soundtracks, and formed the bands Emerson, Lake & Powell and 3 to carry on in the style of ELP. In the early 1990s, ELP reunited for two more albums and several tours before breaking up again in the late 1990s. Emerson also reunited The Nice in 2002 and 2003 for a tour.

During the 2000s, Emerson resumed his solo career, including touring with his own Keith Emerson Band featuring guitarist Dave Kilminster, then replaced by Marc Bonilla, and collaborating with several orchestras. He reunited with ELP bandmate Greg Lake in 2010 for a duo tour, culminating in a one-off ELP reunion show in London to celebrate the band's 40th anniversary. Emerson's last album, The Three Fates Project, with Marc Bonilla and Terje Mikkelsen, was released in 2012. Emerson reportedly suffered from depression, and since 1993 developed nerve damage that hampered his playing, making him anxious about upcoming performances. He died of a self-inflicted gunshot wound on 11 March 2016 at his home in Santa Monica, California.

Emerson is widely regarded as one of the greatest keyboard players of the progressive rock era. AllMusic describes Emerson as "perhaps the greatest, most technically accomplished keyboardist in rock history". In 2019, readers of Prog voted him the greatest keyboard player in progressive rock.