He was an English theoretical physicist, cosmologist, author and Director of Research at the 
Centre for Theoretical Cosmology within the University of Cambridge.
His scientific works include a collaboration with Roger Penrose on gravitational
singularity theorems in the framework of general relativity and the theoretical
prediction that black holes emit radiation, often called Hawking radiation.
Hawking was the first to set out a theory of cosmology explained by a union of the
general theory of relativity and quantum mechanics.
He was the Lucasian Professor of Mathematics at the University of Cambridge
between 1979 and 2009 and achieved commercial success with works of popular
science in which he discusses his own theories and cosmology in general;
his book A Brief History of Time appeared on the British Sunday Times best-seller
list for a record-breaking 237 weeks.

Hawking had a rare early-onset, slow-progressing form of amyotrophic
lateral sclerosis (ALS) that gradually paralysed him over the decades.
He was still able to communicate using a single cheek muscle attached to a 
speech-generating device.

Hawking died on 14 March 2018, at the age of 76.

More details : Wikipedia