Tony Nicklinson's last tweet today read: "Goodbye world the time has come, I had some fun."
The 58-year-old, who had suffered from 'locked in syndrome' following a massive stroke in 2005, died this morning in his family home in Melksham, Trowbridge.
He had last week lost his High Court appeal to enable doctors to legally end his life.
Mr Nicklinson was paralysed from the neck down and vowed last week to appeal the decision that he claimed consigned him to 'yet another period of physical discomfort, misery and mental anguish'.
Shortly after his death at around 10am this morning Mr Nicklinson's family posted a short message on his Twitter account. It said: "You may already know, my Dad died peacefully this morning of natural causes. he was 58."
Five minutes later the family posted another tweet. It read: "Before he died, he asked us to tweet: 'Goodbye world the time has come, I had some fun'."
They then added: "Thank you for your support over the years. We would appreciate some privacy at this difficult time. Love, Jane, Lauren and Beth."
Mr Nicklinson was cared for full-time by his wife Jane, 56. She said on Twitter today that she had "lost the love of my life but he suffers no more."
Beth Nicklinson, Mr Nicklinson's daughter, tweeted: "Couldn't have asked for a better dad, so strong. You are now at peace, we will be fine. I love you xxx."
His older daughter Lauren, 24, tweeted: "Dad, you are finally at peace. Beth and I are so proud to be your daughters, we got our strength from you. I love you xxx."
The family's solicitor Saimo Chahal said: "Jane told me that Tony went rapidly downhill over last weekend, having contracted pneumonia.
"He had made an advanced directive in 2004 refusing any life-sustaining treatment and also refused food from last week.
[Related article: Locked-in man Tony Nicklinson breaks down as he loses right-to-die bid]
A spokesman for Wiltshire Police said there were no suspicious circumstances surrounding his death.
He said: "Police are not involved at all. We can confirm he passed away and it is not a matter for Wiltshire Police.
"His death certificate has been signed by a doctor, so it is not a matter for Wiltshire Police or the coroner."
Shortly after the High Court verdict on Thursday of last week Mr Nicklinson had tweeted to his 47,000 Twitter followers that he was 'still down after [the] result'.
Speaking through his computer following the decision, a tearful Mr Nicklinson had said: "Judges, like politicians, are happiest when they can avoid confronting the real issues and this judgement is no exception to the rule.
"I believe that the legal team acting on my behalf are prepared to go all the way on this but unfortunately for me it means yet another period of physical discomfort, misery and mental anguish while we find out who controls my life, me or the state."
Three judges sitting in London unanimously agreed that it would be wrong for the court to depart from the long-established legal position that "voluntary euthanasia is murder, however understandable the motives may be".
[Related article: Tony Nicklinson dies at 58: Tributes pour in for 'locked in' man]
Mr Nicklinson, a rugby fanatic, was en-route to Athens with business colleagues when he suffered a massive stroke in June 2005.
His wife Jane, a former nurse, rushed from their home in Dubai to the Greek hospital where he lay in a coma.
Mr Nicklinson went from a "larger than life" character to a wheelchair-bound invalid.
He described life as "dull, miserable, demeaning, undignified and intolerable".
The only way he could communicate to his family is via a perspex board and letters - looking, blinking and nodding to spell out words - and he could not move his limbs.