Nicola Walker (born in Stepney, London, United Kingdom) is a British actress, best known for her starring roles in various British television programmes from the 1990s onwards, particularly as Ruth in the spy drama Spooks. Beginning her acting career with the Cambridge Footlights (her contemporaries included Spookswriter David Wolstencroft and comedian Sue Perkins) while at university, her big break came with the leading part of DI Susan Taylor in the ITV thriller serial Touching Evil in 1997, co-starring opposite Robson Green. She also appeared in its two sequel serials in 1998 and 1999.

Also in 1999, she took the lead role in the post-apocalyptic drama serial The Last Train, also screened on ITV (and written by future Spooks writer Matthew Graham). In 2003, she joined the regular cast of the BBC One spy drama Spooks for its second run, and remained with the show until the fifth series, during the production of which it was announced she was expecting her first child and would be leaving. She has also appeared in guest roles in episodes of series such as Dalziel and Pascoe, Jonathan Creek and Broken News. In 2007 she had a prominent supporting role as a child snatcher in the ITV1 drama serial Torn and appeared in the BBC adaptation of Oliver Twist.

In film, her roles have tended to be smaller supporting parts. Her most prominent role has been as the irritating folk singer in Four Weddings and a Funeral (1994). She also appeared in the feature film adaptation of the classic television series Thunderbirds (2004).

Started off in the Cambridge Footlights.