Grumpy Cat, the million-dollar pet who became famous on the internet by virtue of her unusually ill-tempered facial expression has died aged only seven years old.

The cat's real name is Tardar Sauce, and her permanent scowl is a result of her having been born with dwarfism and an underbite.

The animal, from Morristown, Arizona, garnered millions of fans throughout her relatively short life and was estimated to be worth over £70m.

Writing on Twitter, her owner Tabatha Bundesen said: "Some days are grumpier than others", revealing that her beloved animal died in her arms after suffering complications from a urinary tract infection.

The post reads: “Despite care from top professionals, as well as from her very loving family, Grumpy encountered complications from a recent urinary tract infection that unfortunately became too tough for her to overcome,” it continues.

“Besides being our baby and a cherished member of the family, Grumpy Cat has helped millions of people smile all around the world – even when times were tough. Her spirit will continue to live on through her fans everywhere.”