But when will Mr Johnson officially become the prime minister, when will he meet the Queen and how will the reordering of his government take place?
Here’s a look at how the remainder of the week will play out:
– Wednesday 24 July
Theresa May will take her final Prime Minister’s Questions in the Commons before formally resigning as PM.
She is expected to return to Downing Street after her last stint at the despatch box to have lunch and address Number 10 staff.
Mrs May will then make a short statement to media waiting in the street outside the famous black door before heading to Buckingham Palace to offer her resignation to the Queen.
The monarch will then meet the new leader of the Tory party at the Palace and invite him to form a new government.
Traditionally, the new prime minister makes a statement in Downing Street before stepping into Number 10 for the first time as PM.
– Thursday 25 July
The new prime minister will likely spend their first full day in office finalising their Government – with appointments to the Cabinet and ministerial team expected.
The Commons will rise for the summer recess, with MPs not due to return until September 3.
– Friday 26 July
The Cabinet reshuffle could continue into Friday, with the new prime minister finalising their team ahead of the summer.
They may also make their first official visit as PM to one of the four regions of the UK – like Mrs May’s trip to Scotland on her second day in office – or perhaps head to Brussels to in a bid to reopen Brexit negotiations.