Tony Nicklinson, who lost a legal battle last week for the right to end his life with medical help, has died at the age of 58.
Lawyers for Mr Nicklinson said he died at his home in Melksham, Trowbridge, at around 10am on Wednesday.
In a brief statement, Bindmans LLP said: "This is to notify you of the sad death of Tony Nicklinson at approximately 10am this morning."
A tweet posted on his Twitter page read: "You may already know, my Dad died peacefully this morning of natural causes. He was 58."
Last week, the High Court rejected Mr Nicklinson's legal battle for the right to die with medical help.
His wife Jane described the decision as "one-sided", and said at the time they intended to appeal.
A spokesman for Wiltshire Police said the force would not be investigation his death.
"Police are not involved at all. We can confirm he passed away and it is not a matter for Wiltshire Police," he said.
"His death certificate has been signed by a doctor, so it is not a matter for Wiltshire Police or the coroner."