The 42-year-old actress, who plays Michelle Connor in the drama series, has been on the show for 13 years.
She was originally cast for a cameo role, but went on to star in several hard-hitting storylines over the years.
Announcing her resignation, the TV star said: “It’s been an incredibly difficult decision but it feels like the right time.”
She went on to tell The Sun: “When I was lucky enough to be offered four episodes I could never in my wildest dreams have thought I’d be here 13 years later.”
According to the publication, Coronation Street producers are desperate for her to stay on as feisty Michelle.
Executive producer John Whiston said: “Kym has done a fantastic job. She has brought incredible heart and humanity to some hugely important stories.
“We will be really sad to lose her when she goes but totally understand that, after dedicating herself to the show for so long she now fancies trying something else.”
Kym will leave the series later this year, however, show bosses have decided not to kill off her character.
Although she is yet to leave the soap, Kym has already teased her return to the ITV series.
“This isn’t the last you’ve heard of Michelle Connor, she’ll be back!” she exclaimed.
“I can’t wait to see what the writers have in store for the future.”
The soap star’s announcement comes days after she spoke about the 10th anniversary of her son Archie’s death.
Archie, who she had with then-partner Jamie Lomas, died moments after she gave birth in February 2009 after he was born 18 weeks early.
The former Hear’Say singer admitted she was “inconsolable” with grief on the anniversary of his death this year.
In her recent OK! Magazine column, she said: “When I opened my eyes on the morning of his anniversary, I was inconsolable for a while.
“I was more emotional this year, maybe it’s because it’s been a decade. Some years I cope better but this year wasn’t one of them.”
Kym’s eldest daughter Emilie, 21, is currently expecting her first child and she revealed she found “comfort” on the anniversary after hearing her unborn grandson’s heartbeat for the first time.
“Emilie happened to have an antenatal appointment in the afternoon and she asked me to go along with her and hearing my grandson’s heartbeat gave me a lot of comfort,” she explained.
Coronation Street continues tonight on ITV at 7.30pm and 8.30pm.