Harding rose to fame in 2002 after becoming a member of pop group Girls Aloud through British ITV's reality television programme Popstars: The Rivals. They have become one of the few reality television acts to achieve continued success, amassing a fortune of £25 million by May 2009. With Girls Aloud, Harding has been successful in achieving a string of 20 consecutive UK top ten singles (including four number ones), two UK number one albums, and received nominations for five BRIT Awards, winning Best Single in 2009 for "The Promise".
Harding was born in Ascot, Berkshire. She grew up, together with her two half brothers, in Staines, Surrey, then Stockport, Greater Manchester. She grew up in a musical household and has attributed her "musical genes" to her musician father, John Adam Hardman, who introduced her to the studio at a very young age. She attended Hazel Grove High School from 1993 to 1998, and later attended Stockport College where she studied hair.When she was 15, her father left her mother. Harding's parents subsequently divorced; she has no contact with her father.
She then worked as part of the promotions team for 2 nightclubs in The Grand Central Leisure Park in Stockport as well as waitressing at Pizza Hut, driving a van, debt collecting and as a BT telephone operator. She also toured North West England performing at pubs, social clubs, and caravan parks to support herself. In 2002, she was recording dance tracks when she decided to audition for Popstars: The Rivals She auditioned both for being a contestant on UK talent-search shows Fame Academy and Popstars: The Rivals and it was in the latter where she found fame, pulling out of Fame Academy after being accepted in the Popstars 1st round.
On January 2011, Harding and DJ Tom Crane, whom she had been dating since June 2007, announced their engagement. He proposed on New Year's Eve 2010 while on holiday in the Maldives. However, rumours circulated that the couple had called the wedding off, and on September 6th of the same year it was confirmed via the fiancé on his twitter account. It is uncertain if the couple have split permanently as Crane posted "Sarah and I have decided to take a break. I have nothing else to say".