Sir Simon Neville Llewelyn Marsden, 4th Baronet (1 December 1948 – 22 January 2012) was an English photographer and author.

[1] From 1969, he worked as an assistant to Irish photographer Ruan O'Lochlainn, whose wife, Jackie Mackay, was a master printer from whom Marsden learned the skills of the darkroom.

Two grants from the Arts Council of Great Britain in 1975 and 1976 allowed Marsden to undertake extensive journeys throughout Europe, the Middle East, and the United States, photographing the architectural subjects and varied landscapes he encountered.

[2] In 2003 Simon Marsden collaborated with director Jason Figgis on The Twilight Hour – Visions of Ireland's Haunted Past.

It was nominated for two Irish Film and TV Academy Awards, was screened on Ireland's national broadcaster RTE as part of their Arts Lives series and ran for three years on Discovery Civilisations across 100 countries.