David Martijn Westerholt (born 30 March 1979 in Waddinxveen, Netherlands) is the cofounder (along with Charlotte Wessels), keyboardist, and the main songwriter of the Dutch symphonic metal band Delain. He was previously a member of symphonic metal band Within Temptation, until he was diagnosed with infectious mononucleosis shortly after the release of Within Temptation's second full-length studio album, Mother Earth.