The 40-year-old star took home the gong for best female dramatic performance for her heartbreaking portrayal of Coronation Street's devastating miscarriage storyline.
The emotional performance had roots in Kym's personal life as she suffered the devastating loss of her son when he was born prematurely just 23 weeks into her pregnancy.
Taking to the stage at the Lowry Theatre, Kym dedicated the accolade to Archie in an emotional speech, saying: "This award I would like to dedicate to my son Archie and all those angel babies.
Coronation Street's Kym Marsh dedicated her British Soap Award to her late son
Kym made an emotional speech about her heartbreaking Coronation Street stillbirth storyline Emmerdale's most shocking moments Thu, January 5, 2017
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"Michelle and Steve's baby loss story was perhaps the most difficult thing I've had to do in my career," she continued. "It took us to places we didn't want to go to again but we did it because it's such an important story to tell."
The actress added that the show was "breaking the silence" with the tragic storyline and "making people realise they are not alone".
Elsewhere, Emmerdale scooped the big award of the night, taking home six gongs in total including one for the best British soap, beating Doctors, EastEnders, Coronation Street and Hollyoaks for the coveted title.
Emmerdale won six awards at the star-studded ceremony
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Emmerdale's John Middleton won the best actor gong
Meanwhile, John Middleton, 63, won the best actor award for his role as Ashley Thomas and his on-screen wife Charlotte Bellamy, who plays Laurel, took home best actress.
Best comedy performance went to Coronation Street's Dolly-Rose Campbell for her role as Gemma Winter, and her co-star Elle Milvaney, 14, was awarded best young actor for her incredible performance as Amy Barlow.
After it was revealed that he had pushed his father Ken Barlow (played by Bill Roache), Daniel Osbourne actor Rob Mallard, 25, was crowned the best newcomer.
The British Soap Awards air Tuesday at 8pm on ITV.