Tony Nicklinson, a man with locked-in syndrome who fought for the right for doctors to legally end his life, has died.
The 58-year-old was paralysed from the neck down after suffering a stroke in 2005 and wanted a doctor to be allowed to terminate his life.
Last week Mr Nicklinson, from Melksham, Wiltshire, lost his High Court case to allow doctors to end his life.
His solicitors said he died at about 10:00 BST.
In a brief statement, law firm Bindmans LLP said: "This is to notify you of the sad death of Tony Nicklinson at approximately 10am this morning."
The father-of-two was left paralysed with locked-in syndrome after suffering a stroke while on a business trip to Athens.
He said he was "devastated" by the court's decision and would appeal against it.
Messages sent from Mr Nicklinson's personal Twitter account said: "You may already know, my Dad died peacefully this morning of natural causes. he was 58.
"Before he died, he asked us to tweet: 'Goodbye world the time has come, I had some fun'.
"Thank you for your support over the years. We would appreciate some privacy at this difficult time. Love, Jane, Lauren and Beth."
A message sent from the Twitter account of Mr Nicklinson's daughter Beth said: "RIP @TonyNicklinson. Couldn't have asked for a better dad, so strong. You are now at peace, we will be fine. I love you xxx"
Some are born great, some achieve greatness and some have greatness thrust upon them.
The rest of us are a bit crap.