Stephen Hawking
The illness left him in a wheelchair and largely unable to speak except through a voice synthesiser.
In a statement his children, Lucy, Robert and Tim, said: "We are deeply saddened that our beloved father passed away today.
"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."
A book of condolence has been opened at Gonville and Caius College in Cambridge, where Prof Hawking was a fellow.
Prof Hawking was the first to set out a theory of cosmology as a union of relativity and quantum mechanics.
He also discovered that black holes leak energy and fade to nothing - a phenomenon that would later become known as Hawking radiation.
“Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist,” Hawking said of the meaning of life. “Be curious. And however difficult life may seem, there is always something you can do and succeed at.”
don't forget Stephen Hawking's books
1.My Brief History
2.A Brief History of Time
3.The Grand Design
4.Black Holes: The Reith lectures
George and the Blue Moon
5.The Universe in a Nutshell