Louise played the role of hairdresser Julie Cooper in EastEnders back in 1989 but went on to perform in the West End, as Donna in Mamma Mia and later Madame Morrible in the musical Wicked.
Her cancer diagnosis in 2013 forced her to step off the stage.
The tragic news of her death was announced on a Facebook page dedicated to raising money for the actress' cancer treatment.
'Dear wonderful supporters of Louise, I am so sorry to have to let you know what an hour ago we lost Louise to that horrid disease', the Facebook statement said.
'All of her family were with her. The world has lost a truly special person, prodigiously talented, and a friend to all. Can I thank all of you who joined us in this battle and who helped Louise to have hope.'
Louise Plowright â€“ Forever our Dancing Queen, always in our hearts x pic.twitter.com/7Yfpmes17B— MAMMA MIA! (@MammaMiaMusical) March 1, 2016
Louise joins a list of stars who've passed away from cancer this year, including Alan Rickman, David Bowie and Sir Terry Wogan.
Louise was first diagnosed with cancer in 2012, but after going into remission, her cancer returned at the beginning of last year.
Last November, the actress took to Facebook to thank everyone for their fundraising efforts. Thanks to the campaign, Louise went to Seoul, South Korea, to receive treatment after doctors in the UK advised there was nothing else they could do when the cancer returned.
'I'm absolutely thrilled that this wonderful concert has been organised on behalf of myself and Pancreatic Cancer research. My only wish would be that I could take part in it too, maybe next year. Every day when I'm receiving treatment I'm reminded that no matter how wonderful the NHS is, this would not have been possible in the UK - yet!!'
The West End performer also gave details of her road to recovery, saying there is 'nothing certain about tomorrow'.
'This is a long journey, recovery and cure could take much much longer. At present I only embrace the moment, for there is nothing certain about tomorrow', Louise wrote last year.
'Eventually though, this is all going to be part of a bigger picture. I'm learning so much and it will be my mission to get Dr Moon to the UK to speak with our eminent oncologists about his ground breaking treatment so that one day anyone diagnosed with the 'death sentence', that is Pancreatic cancer, can live with hope.'
Our thoughts are with Louise's family and friends.