Tara-Lynne O'Neill (born 16 November 1975) is a film, theatre and television actress from Northern Ireland.

During her childhood, she aspired to become a dentist, but abandoned this after failing her General Certificate of Secondary Education in chemistry.

At sixth-form college, she opted for a career in acting.

O'Neill started work as a television presenter on Saturday Disney from 1993 to 1996. She was also a main presenter on The Over the Wall Gang, a young people's television show from BBC Northern Ireland

O'Neill also appeared in film roles such as the town's seductress in The Most Fertile Man in Ireland (1999), and as Claire McKee in Wild About Harry (2000). She later played Joanne Ryan in EastEnders, appearing in 58 episodes between 20 September 2002, and 21 August 2003.

Between 2013 and 2016, she appeared in The Fall. In 2018, she joined the main cast of Derry Girls as Mary Quinn, remaining on the show until the airing of the final episode on 18 May 2022. In April 2024, O'Neill was cast as Inspector Eve Dunlop in BBC's Hope Street for the show's fourth series.

Her other roles include The Informant (1997), Disco Pigs (2001), Full Circle and Omagh (2004).