Sources have said that Her Majesty has been left "devastated."
One of the puppies given to the Queen to keep her company while Prince Philip was in hospital has died.
Fergus, a dorgi gifted to the Queen by her son Prince Andrew, was only around five months old and sadly passed away at the weekend.
Mail Online reports that sources have said the Queen has been left "devastated" by its passing. It comes just two months after she said goodbye to her husband Prince Philip at his funeral.
It is not known how the dorgi - a Dachshund and a Welsh Corgi mix - died.
Her Majesty named him Fergus after her maternal uncle Fergus Bowes-Lyon, who died in France whilst fighting in World War One.
Prince Andrew gave his mother a second dog, a corgi called Muick, alongside Fergus in a bid to cheer her up whilst Philip was in hospital recovering from heart surgery.
A source told the
Sun: "The Queen is absolutely devastated.
"The puppies were brought in to cheer her up during a very difficult period.
"Everyone concerned is upset as this comes so soon after she lost her husband."
Just a few months ago the Queen lost another of her beloved pets, Vulcan, who was also a dachshund-corgi cross. Vulcan had been the Queen's pet since 2007. He died a few weeks before Christmas.
Throughout her reign, the Queen has owned more than 30 pets. However, in 2015 an informal advisor to Her Majesty said that she would no longer be replacing her corgis as she did not want to leave any behind when she dies.
