Stephen Hawking has died at the age of 76, his family has said.
The British physicist was known for his work with black holes and relativity, and wrote several popular science books including A Brief History of Time.
"We are deeply saddened that our beloved father passed away today," a family statement said.
At the age of 22 Stephen Hawking was given only a few years to live after being diagnosed with a rare form of motor neurone disease.
The illness left him wheelchair-bound and largely unable to speak except through a voice synthesiser.
His family said that he died peacefully in his home near Cambridge University, where he did much of his ground-breaking work on black holes.
In the statement his children, Lucy, Robert and Tim said: "He was a great scientist and an extraordinary man whose work and legacy will live on for many years."
They praised his "courage and persistence" and said his "brilliance and humour" inspired people across the world.
"He once said, 'It would not be much of a universe if it wasn't home to the people you love.' We will miss him forever."
Prof Hawking was the first to set out a theory of cosmology as a union of relativity and quantum mechanics.