Jonny Greenwood is a lead guitarist in the British alternative band Radiohead. He also plays piano, organ, viola, synths, Glockenspiel, harmonica and the Ondes Martenot, among a host of other devices used to "enhance" the soundscape of many Radiohead songs.

He also utilizes modular synthesizers, a Korg Kaoss Pad, and a laptop (for voice clips/modulation) on newer tracks. Jonny is one of the most prominent users of the Ondes Martenot, an early electronic musical instrument with a keyboard and slide that composer Olivier Messiaen is famous for using. Jonny uses the Ondes Martenot on the soundtrack to the film Bodysong.

Apart from his work with Radiohead, Greenwood is also a composer and has produced several neo-classical works as part of his tenure as the BBC's composer-in-residence. He also composed the soundtracks to the films Bodysong (2003) and There Will Be Blood (2007).