Internet sensation Grumpy Cat, who became famous for her permanent frown, has died aged seven, according to her owners.

The family announced the news in a statement posted to social media with the caption: ‘Some days are grumpier than others’.

They said they are "unimaginably heartbroken to announce the loss of our beloved Grumpy Cat" at their home in Arizona.

The mixed-breed cat, whose real name is Tardar Sauce, shot to fame in 2012 after a photo of her went viral and spread around the world as a meme.

Her website says: "Her petite size and famous face is likely due to feline dwarfism and her rear end wobbles a bit when she walks due to this; otherwise she is a perfect little kitty!"

The cat, one of the most famous felines in the world, has 8.5 million fans on Facebook, 2.4 million followers on Instagram and 1.5 million followers on Twitter. She also appeared on television shows and travelled around the world making appearances.

She has been photographed with celebrities including Stan Lee and Jennifer Lopez, and a model of Grumpy Cat was even introduced at Madame Tussauds in San Francisco.

"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," said the family.

"Her spirit will continue to live on through her fans everywhere."

Grumpy Cat died from complications associated with a recent urinary tract infection "despite care from top professionals," said the family.