The former PM - ousted by his own MPs in July - has signed a lucrative book deal with Harper Collins to detail his stint in No10.
No publication date has yet been set or details of the money involved have been disclosed.
HarperCollins chief executive Arabella Pike said: “This will be a prime ministerial memoir like no other. I look forward to working with Boris Johnson as he writes his account of his time in office during some of the most momentous events the United Kingdom has seen in recent times.”
The deal answers one question about what the ex-PM would do next after he was forced out of office by his own cabinet.
The 58-year-old had a chance to emulate his political hero, Winston Churchill, and return from the wilderness and stand in the Tory leadership election last October just seven weeks after leaving Downing Street.
But Johnson was forced to admit he could not unite his warring party, and surrendered the race to his ex-chancellor, Rishi Sunak.
Johnson’s time in office was punctuated by a series of scandals and the Covid-19 pandemic, with any memoir also likely to detail his efforts to “Get Brexit Done”.
Previous prime ministers have made considerable amounts of money through book deals.
Sir Tony Blair was reported to have been paid “up to £5 million” in 2007 for his political memoir A Journey, while David Cameron was reported to have earned £1.5 million for his memoir, For The Record.
The new memoir will be the latest book penned by former journalist Johnson, who has authored several books throughout his career .
In 2014, he published ‘The Churchill Factor’, a biography of his hero and wartime leader Sir Winston Churchill.
As a backbench Conservative MP Johnson has also made a considerable amount of money touring the speaking circuit, declaring more than £1 million in speaking fees since leaving office in September.
Johnson is hoping his book does better that his disgraced former health secretary Matt Hancock who went on I’m a Celebrity… Get Me Out of Here! in an attempt to rehabilitate his image.
Hancock’s tome, The Pandemic Diaries: The Inside Story of Britain’s Battle Against Covid, was released on December 6.
According to official figures, it only shifted 3,304 copies in the first week – and just 600 in the second.