The screenwriter and director was born and still lived in Leeds, where she set and filmed many of the hit shows she wrote. She was the creative force behind BBC and ITV series such as The Syndicate, Fat Friends, Girlfriends, Love, Lies and Records and The Chase.
The mother of two had her first child in her teens and went to Bretton Hall College of Education in Wakefield when her daughters were at school before launching her career in the television industry.
Actress Lisa Riley said: "Dearest Kay - what a massive shock to hear this news, you have been taken far far far too young. You were the best boss to work for, you embraced all that is good about our industry, believing in talent."
ITV Calendar presenter Duncan Wood added: "Devastating news, can’t believe it. Kay was a phenomenal writer, producer, director who brought groundbreaking work to the screen. My deepest sympathy to all her family and friends."
Leeds Civic Trust posted: "Kay Mellor, a true friend of the Trust and a champion of Leeds and the North. Thank you for your incredible contribution to our city. We send our deepest sympathies and condolences to the family."
Author June Taylor commented: "Such sad news. Kay Mellor was a force for good representing the North both on and off the tele. Always admired her for staying in Leeds, not getting sucked into the London vortex. She was one of the reasons I started to believe in my own writing dream. Thank you."
Top Gear producer Ian Brown said: "One of TV's top writers. My thoughts are with her family. I was lucky enough to write Kay's This Is Your Life show. No pressure. So many credits creating so much drama, entertainment and employment."
Screenwriter Rebekah Harrison posted: "Shocked and devastated by the news - she was truly an inspiration to me - paving the way for working-class women and our stories on TV. I was in awe of her talent and tenacity, relentlessly championing new writers. I wouldn’t be the writer I am without Kay."
Actor Lenny Henry said: "I was saddened to hear that Kay Mellor has died. I was lucky to work with her on The Syndicate and found her to be incredibly creative, funny and instinctive. She knew what she wanted and knew how to get the best from us as actors. She will be missed. Condolences to her family."
BBC presenter Peter Levy wrote: "So sad to hear the death of Kay Mellor. She was a powerhouse for the writing and acting world in Yorkshire. So many owe work and careers to her. In the 80s I moaned on air how awful Albion Market was, she was listening and she wrote it! She came on air and we hit it off. RIP."