Date of Birth: 22 September 1961
Job: Conservative MP
Education: St Bride's High School, East Kilbride, and Glasgow University
Family: Married, no children
On his party's future: "We can't allow the Conservative leadership campaign to be dominated by the issues in the referendum. There are many other issues I care very passionately about. As a doctor I care a great deal about what happens to our healthcare in this country. As a former defence secretary, I care about what happens to our armed forces and I think we need to paint an optimistic picture for our country," he told Iain Dale on LBC radio.
Where he stands on Brexit: "I do not believe there is room for membership of the single market if it entails free movement of people. Those who voted to leave the EU would regard it as a betrayal and frankly they would be right. We do not need to be part of the single market to sell into it. Countries like the United States manage to do that very well. It is in our mutual interests to have a free and open trade relationship with our European partners but we cannot accept the concept of free movement of people as its cost."
When he would trigger Article 50: Has called for a "period of calm" and reflection before starting the process of leaving the EU. Has said the UK should aim to leave on 1 January 2019.
Free movement policy: "I do not believe there is room for membership of the single market, if it entails free movement of people," he says. He would seek an agreement where EU citizens currently living in the UK would be granted "full rights to remain" as part of a mutual agreement allowing UK citizens to continue living and working in the EU, but a different arrangement would apply in the future.
What the press says: "Fox is a hero to the many Conservatives who not only revere the memory of Margaret Thatcher, but also believe that unabashed Thatcherism is what is required now. They praise Fox for sounding 'principled' rather than 'wishy-washy'. They laud him for being 'a proper Eurosceptic' who wants strict immigration controls. They love his loyalty to old friends, and deep commitment to the Anglo-American relationship. They admire him as a communicator, relish his joie de vivre." Author Andrew Gimson, ConservativeHome.
Liam Fox has worked hard over the years to build up a powerbase on the right of the Conservative Party.
He failed in his bid to be party leader in 2005, after narrowly failing to secure enough support from MPs to go through to the vote of the membership, which was between David Davis and David Cameron.
He was rewarded with a cabinet position by Mr Cameron but was forced to resign as defence secretary in 2011 after allowing his friend and best man Adam Werritty to take on an unofficial and undeclared role as his adviser.
He was ordered to repay £3,000 of expenses for allowing Mr Werritty to live rent-free at his London home for a year.
The 54-year-old has spent his time in the wilderness writing - in 2013 he published Rising Tides: Facing the Challenges of a New Era, in which he argued that that world's institutions are not equipped for the economic and security challenges of the 21st Century - and plotting his return to the political front line.
He voted against gay marriage, and in 2013 called for the Guardian newspaper to be prosecuted over its role in the Edward Snowden leaks. He accused the newspaper of collaborating in "indiscriminate publication" of material that damaged national security.
He played a prominent role in the campaign to get Britain out of the EU, warning young people that "uncontrolled migration" would make it "harder to get a home of your own".
Born in East Kilbride, South Lanarkshire, Mr Fox attended a local comprehensive school before going on to study medicine at Glasgow University.
After working as a GP in Somerset and Buckinghamshire and as a civilian army medical officer, he successfully contested the rural Somerset seat of Woodspring, now North Somerset, in 1992.
A gregarious and approachable figure with a talent for self-promotion, Mr Fox was mentioned in the sleeve notes of the debut album of his friend Natalie Imbruglia, sparking rumours of a romance with the ex-Neighbours star.
In 2005 he married long-term girlfriend Jesme, a fellow doctor from the same area south of Glasgow.