But who is BoJo? Real name, Alexander Boris de Pfeffel Johnson.
Throughout his career, Mr Johnson, 55, has been known for his media gaffes, including getting stuck on a zip-line during a 2012 event in London and taking out a 10-year-old boy with a rugby tackle in 2015.
One of the more serious gaffes was in 2017 when as UK foreign secretary he erroneously said that a Briton detained in Iran was training journalists in the region. His comment resulted in Nazanin Zaghari-Ratcliffe getting hauled in front of an Iranian court and told her sentence could be doubled.
Her husband was recently on a hunger strike to campaign for the 40-year-old’s release.
In August 2018, Mr Johnson was rebuked by Theresa May after he compared women wearing burqas and niqabs to letter boxes and bank robbers. And earlier this year, he offended child abuse survivors by claiming that government money spent on historical investigations had been "spaffed up a wall".
Mr Johnson also once described the continent of Africa as "that country" and offended Papua New Guinea’s high commissioner in London by comparing the Labour Party with "Papua New Guinea-style orgies of cannibalism and chief-killing”.
In recent days, he has come under fire for saying Islam caused the Muslim world to be "literally centuries behind" the west.
Despite Mr Johnson’s attempts to keep his family life private, a recent spat with his girlfriend Carrie Symonds became headline news after neighbours called the police to their place of residence.
Mr Johnson was later asked whether his campaign had leaked a happy photo of him and his partner in an attempt to spin the story.
Source: Daily Mirror/Daily Telegraph/The Daily Mail UK
Mr Johnson is a father of four adult children with his estranged second wife Marina Wheeler.
Lara Lettice, Milo Arthur, Cassia Peaches and Theodore Apollo are all in their twenties. He has refused to answer questions about them, saying it would be "unfair" to "drag them into things".
Speculation about how many illegitimate children Mr Johnson may have started after an appeal court ruled recently that the public had the right to know about a child he fathered during an extramarital affair.
Born in New York to British parents, the would-be prime minister was named Alexander Boris de Pfeffel Johnson.
The family soon returned to Britain where the young Boris was schooled at some of Britain’s best establishments. At Eton, he met the former prime minister David Cameron and he proceeded to the University of Oxford to study classics, and he became a member of the Bullingdon Club, an exclusive all-male club for very wealthy undergraduates.
In 2008, the BBC's Who Do You Think You Are? revealed Mr Johnson is a distant relative of the Queen.
Before entering politics, Boris Johnson made his name as a reporter and a columnist. He was sacked from the Times for making up a quote.
As Brussels correspondent for The Daily Telegraph, he relished in making fun of the EU and creating controversy with his stories.
In 2005 he told the BBC he enjoyed "chucking these rocks over the garden wall" and listening "to this amazing crash from the greenhouse next door in England."
Entering political life
His first attempt at parliament failed in 1997, but Mr Johnson found success in running as MP for Henley in Oxfordshire.
After a brief sacking for an extramarital affair, Mr Johnson staged a comeback in 2005. With the help of Australian electoral strategist Lynton Crosby, he was voted in as mayor of London in 2008.
He led the city through the success of the 2012 London Olympics and introduced a bike-share plan dubbed the 'Boris Bikes'.
Mr Johnson summarises his own achievements during those years on the Conservative party's website. "As the Mayor of our city since 2008, I have cut crime, cut City Hall’s share of council tax and brought jobs and investment to London," he wrote.
Mr Johnson first attempted to become prime minister back in 2016 when David Cameron resigned over Brexit.
Theresa May duly appointed him foreign secretary but he tendered his resignation on 9 July 2018, citing his disagreement with Ms May's Brexit plan.
Mr Johnson has gained a lot of support for saying he is prepared for Britain to leave the EU with no deal by 31 October deadline as a last resort.
Chancellor Philip Hammond has warned his policy could cost the British economy as much as 90 billion British pounds. But according to Dr Ben Wellings, his stance on Brexit was a key factor in why he became Britain's prime minister.
"He's telling people what they want to hear - that Britain will get out. Jeremy Hunt is sort of saying: well yes, we'll get out, but I'm not going to commit to an October 31 deadline because we're negotiating - and I think the Conservative membership has had enough of that approach with Theresa May. They just want someone to crash through now."
On Australia Day 2014, Boris Johnson was made an honorary Australian for his services to Australians in London.
During his last visit to Australia in 2017, the then foreign secretary delivered a well-received humorous speech at Sydney Town Hall, highlighting the shared cultural reference points between the two countries and citing Australia’s economic growth and GDP success as a model for Britain to leave the EU.
“So when we look at the forward momentum of Australia in the last few decades you can perhaps see why we in Britain are inclined to take with a pinch of salt some of the very slight gloom and negativity that is emanating from some distinguished quarters about the decision of the British people to leave the European Union,” he said.
More recently he has said he would like to bring in an "Australian-style" points-based visa system to manage immigration to the UK post-Brexit.
"Not that it [Britain] doesn't have one that is similar already, but it plays out quite well amongst people who want immigration to be reduced," Dr Ben Wellings said.
"The sting in the tail is that it was certainly easier to reduce immigration from outside the EU than in it - this used to negatively impact on Australians."
Since his time as London mayor, Mr Johnson has advocated the idea of an Australia-Britain common travel area. His idea had a wary response from Canberra amid concern over the potential number of Britons who would seek to come.
Dr Wellings said it could result in the so-called brain drain of Australian talent to British shores.
"Whatever happens, when Britain leaves the European Union it will still need migrant labour; and it will still need professional and unskilled migrant labour. And so what I think what we will see is a slightly greater emphasis on Australia for a source of skilled labour than currently. Which is of course is not necessarily good for Australia because it might entice our trained professionals to up sticks and leave Australia and go work in London."
Mr Johnson's other idea of creating a free-trade agreement and amalgamating the navies of Australia, Canada, New Zealand and the UK to create an "Indo-Pacific fleet" received a warmer response from Australian government officials.