The former Girls Aloud singer will play a feisty character who's going to make life difficult for troublemaker Tracy Barlow.
She said: "I am excited to be joining Coronation Street. As a fan of the show it is a huge honour for me to join the cast. I can't wait to get started."
Filming for Harding's part will start in May.
The 33-year-old has appeared in films like St. Trinian's, St Trinians 2: The legend of Fritton's Gold (she sang three tracks on the film's soundtrack), Run for Your Wife and Bad Day.
She's also been in BBC television film Freefall as well as taking part in gymnastics competition Tumble and modelling lingerie for Ultimo.
Corrie producer Stuart Blackburn said: "Sarah is proving to be a gifted and exciting actor and I'm absolutely delighted to have her on board, the viewers are in for a treat as her character will be right at the heart of a massive new story for the Barlows."
Harding was part of Girls Aloud from 2002 until they split up after a worldwide reunion tour in 2013.
The star went into rehab in 2011 for depression and alcohol addiction and was banned from driving in 2013 for six months for swerving into the path of a policeman on a bicycle in London.
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Sarah Harding's going to appear in four episodes of Coronation Street later this year.