Tina O'Brien (born 7th August 1983 in Rusholme) has appeared as Sarah Platt on Coronation Street from October 1999 to January 2008 and from March 2015 onwards. She is the third actress to play the role, taking over from Lynsay King, who had made her final appearance as the character in the same month as O'Brien's debut. O'Brien also appeared in Coronation Street: Pantomime.

Before taking over the role of Sarah, she appeared in Children's Ward and Clocking Off, where her character's brother was played by her future Coronation Street half-brother David's actor, Jack P. Shepherd. She also appeared in ITV's Dick Whittington pantomime in 2002. After leaving Coronation Street in 2008, she appeared in Blue Murder, The Secret Diaries of Anne Lister, Accused, Waterloo Road, Call the Midwife, Crime Stories, Doctors and Casualty.

She won the award for Best Newcomer at the 2000 National Television Awards and the award for Best Storyline at the British Soap Awards in the same year.

O'Brien is co-founder of The Drama MOB, a theatre school which has included Seth & Theo Wild as students, along with its successful casting agency The Drama MOB Management, which has represented the Wild twins, Freddie & Isaac Rhodes and Emmanuel & Jeremiah Cheetham.

She is godmother to twins Amy & Emily Walton, who appeared as her on-screen daughter Bethany between 2000 and 2007. She dated Bruno Langley who appeared as her character's boyfriend Todd Grimshaw, before dating Ryan Thomas who appeared as her character's boyfriend and husband Jason Grimshaw. O'Brien and Thomas have a daughter together, Scarlett, who was born in 2008. O'Brien gave birth to her second child, Beau, in 2014 with partner Adam Crofts.