Former Liberal Democrat leader Charles Kennedy has died at his home aged 55, his family said.
The Scottish ex-MP's death was not believed to be suspicious and the cause of death has yet to be confirmed.
Mr Kennedy lost his seat in the Ross, Skye and Lochaber constituency to the SNP's Ian Blackford in last month's general election.
A statement released on behalf of his family said: "It is with great sadness, and an enormous sense of shock, that we announce the death of Charles Kennedy.
"Charles died at home in Fort William yesterday. He was 55. We are obviously devastated at the loss.
"Charles was a fine man, a talented politician, and a loving father to his young son. We ask therefore that the privacy of his family is respected in the coming days.
"There will be a post-mortem and we will issue a further statement when funeral arrangements are made."
A spokesman for Police Scotland said: "Police officers attended an address at Fort William on Monday, June 1 to reports of the sudden death of a 55-year-old man. Police were notified by ambulance service personnel.
"There are no suspicious circumstances and our report will be submitted to the procurator fiscal."
An MP since 1983, Mr Kennedy had previously taken the party to its best election result since the 1920s at the 2005 contest.
His political career began in the Social Democratic Party, winning the Ross, Cromarty and Skye seat to become the youngest MP of the time at the age of 24.
Taking over from Paddy Ashdown in 1999, he went on to lead the party through its most successful period.
His leadership was marked by his opposition to the 2003 invasion of Iraq, which helped propel the Liberal Democrats to their best result in more than 80 years with 62 seats.
Clegg pays tribute
Nick Clegg paid tribute to his predecessor as Liberal Democrat leader: "Charles's untimely death robs Britain of one of the most gifted politicians of his generation.
"Charles devoted his life to public service, yet he had an unusual gift for speaking about politics with humour and humility which touched people well beyond the world of politics.
"He was a staunch internationalist and passionate believer in Britain's role in Europe, yet he was a proud Highlander, Scot and British parliamentarian.
"He was one of the most gentle and unflappable politicians I have ever known, yet he was immensely courageous too not least when he spoke for the country against the invasion of Iraq.
"He led the Liberal Democrats to our party's greatest electoral successes, yet he always remained modest about his huge achievements.
"Whenever I asked him for advice, he was unfailingly kind and wise," the former deputy prime minister added.
"Most of all, I will never forget the pride and love with which he would talk about his own family, most especially his devotion to his son Donald.
"My heart goes out to his sister and brother and to Sarah and Donald at this tragic time."
Mr Kennedy's predecessor as Liberal Democrat leader, Lord Ashdown, said on Twitter: "Charles Kennedy. In a political age not overburdened with gaiety and good sense, he brought us wit, charm, judgement, principle and decency."
Liberal Democrat leadership hopeful Tim Farron MP tweeted: "I am utterly heartbroken about the news of Charles' passing. He was a colleague, friend and mentor. We've lost a giant today."
But in January 2006 - following months of rumours about his drinking - Mr Kennedy dramatically admitted he had been receiving treatment for an alcohol problem and said he was calling a leadership contest.
While he declared that he wanted to carry on he was forced to stand down in the face of the threat of mass resignations by senior colleagues.