Sarah tragically died last September, aged just 39, after losing her battle with cancer.
The Girls Aloud gang were all devastated by the news and are now honouring the memory of their beloved bandmate.
Taking to Instagram, Cheryl said: "Around this time last year when Sarah was really sick, we were desperately trying to find way to help and comfort her. You feel so helpless at times like that. One of the only things she really wanted was a gala dinner.
'While that's underway and we are doing that, we felt like we could be doing more. We've decided to do Race for Life for Sarah at Hyde Park on 24th July.
"I know so many of you want to support her and we'd really love it if you could join us. Walk with us for five miles, but also don't worry if you can't join us, people are doing it virtually too.
"I hope to see you there."
The Race for Life website says: "Many of you will have been touched by Sarah Harding’s cancer story. Join Girls Aloud’s Cheryl, Nadine and Nicola as they Race for Life for Sarah on Sunday 24 July 2022 at Hyde Park, London.
"For those who can’t be in London like Kimberley or who can't attend the event, you can still take part by doing a Race for Life at Home in memory of Sarah whenever it suits you."
Cheryl's Instagram page is full of pics of Sarah, including a beautiful montage of the star posted on what would have been her 40th birthday.
The mum-of-one captioned the video: "Memories may be all we’re left with, but they’re enough to last a lifetime."
Sarah's mum, Marie, broke the heartbreaking news her daughter had passed away on September 5 last year.
Taking to Instagram, she wrote: “It’s with deep heartbreak that today I’m sharing the news that my beautiful daughter Sarah has sadly passed away. Many of you will know of Sarah’s battle with cancer and that she fought so strongly from her diagnosis until her last day.
"She slipped away peacefully this morning. I’d like to thank everyone for their kind support over the past year. It meant the world to Sarah and it gave her great strength and comfort to know she was loved.
"I know she won’t want to be remembered for her fight against this terrible disease – she was a bright shining star and I hope that’s how she can be remembered instead.”
Upon hearing the devastating news, Cheryl said: "Although we knew this day would arrive I am somehow still feeling at a loss for words that our stunning, unique, crazy, quirky, kind and soft-hearted girl has departed."
The link to Race for Life for Sarah can be found here.