David Martijn Westerholt (born 30 March 1979) is a Dutch musician.

He is the founder, keyboardist and main songwriter of the symphonic metal project 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.

His brother Robert is the guitarist and founder of Within Temptation.

He has lived in Zwolle, since studying Communication at Windesheim College in 1998.

In September 2021, Westerholt formed a new symphonic project called Eye of Melian.