David Llewellyn is a Welsh novelist and script writer. He grew up in Pontypool and graduated from Dartington College of Arts in 2000. His first novel, Eleven, was published by Seren Press in 2006. His second, Trace Memory, a spin-off from the BBC drama series Torchwood, was published in March 2008. Everything Is Sinister was published by Seren in May 2008. He has written two novels for the Doctor Who New Series Adventures: The Taking of Chelsea 426, featuring the Tenth Doctor, and Night of the Humans, featuring the Eleventh Doctor and Amy Pond.

In addition to writing novels, Llewellyn wrote the Bernice Summerfield audio play Paradise Frost and the Dark Shadows audio drama The Last Stop for Big Finish Productions.

Llewellyn lives in Cardiff.