Tina Michelle O'Brien (born 7 August 1983) is an English actress and model. She is best known for her role as Sarah Platt in the ITV soap Coronation Street from 1999 to 2007 and 2015 onwards, and her role as Bex Fisher in the BBC school drama Waterloo Road from 2010 to 2011.
Born in Rusholme, Manchester, England, O'Brien left Trinity C.E. High School with nine GCSEs. She starred in the drama Children's Ward in 1997, The Cops in 1998 and Clocking Off in 2000, playing the on-screen half sister of actor Jack P. Shepherd who later became her on-screen brother David Platt in Coronation Street. At the age of sixteen, she joined Coronation Street in October 1999, taking over the role of Sarah-Louise Platt from actress Lynsay King (she was three years older than her character). Sarah's pregnancy with baby Bethany Platt won O'Brien Best Storyline at the British Soap Awards. She has also won Best Newcomer at the National Television Awards, and the TV Quick Awards. O'Brien revealed in the British press in April 2007 that she would be leaving Coronation Street before the end of the year. Her first role after leaving Coronation Street was in the 2007 pantomime at Manchester Opera House, where she played the title character of Cinderella. Her first television role post-Coronation Street was in the ITV police television drama Blue Murder, filmed whilst four months pregnant, in which she played a character called Amy Kirkland. O'Brien expressed interest in doing televised dramas and theatre work, although after becoming pregnant, she decided to put her career on hold.