Pudsey was the first dog to win Britain's Got Talent, going on to become a star with his owner and even starring in his own movie in 2014 - with his voice provided by Britain's Got Talent judge David Walliams.
Ashleigh has told how putting Pudsey down was the most hard decision of her life, as she made an emotional tribute to her beloved pet.
After Pudsey's short battle against leukaemia, I had to make the hardest decision of my life to let my attractive boy go to sleep.
Butler said that while she and Pudsey only had 11 years together, "they were the best years ever".
"We so wanted to bring him home to the place where he was born and lived his whole life, but he was too ill to make the journey home from Davies vets".
"No words can express just how much I will miss him".
Pudsey died at the age of 11 following a leukaemia diagnosis, five years after the pair won the ITV talent contest.More news: 'Dunkirk' conquers weekend with US$50.5m 'Valerian' flops
She described him as her "one in a billion dog that will never be replaced".
"Pudsey will always be in everyone's hearts, he was an wonderful dog", added another.
While Pudsey's talent and Ashleigh's skill certainly set them on course for a big win at the time, the bond they shared is what kept members of the public captivated years later.
The pair from Wellingborough in Northamptonshire, came to fame in 2012 after wowing judge Simon Cowell with their Mission Impossible inspired performance.
"My heart is broken, and I don't know how I'm going to get through this".
They performed for The Queen at the Royal Variety Performance and in 2012, Pudsey won a £100k book deal for the publication of his his autobiography.
The BGT official channel said: "We are saddened to hear that today we lost Pudsey, a most marvellous victor".
Our thoughts go out to Ashleigh and Pudsey's family.