Either Rishi Sunak or Liz Truss, the final two candidates hoping to replace Mr Johnson, will soon take over the top job.
But what time will the new prime minister be announced and how will it happen?
When will the new prime minister be announced?
The result is due to be announced on Monday, September 5. The new prime minister will be announced at 12.30pm in Westminster, in front of MPs and peers.
Chairman of the 1922 Committee of backbench MPs, Sir Graham Brady, will announce the result of the contest.
What was the voting process?
The voting process took part in two stages.
In stage one, Conservative MPs choose two candidates to put forward to stage two. This takes place through a series of votes, and is how the field has been narrowed down to Truss and Sunak. Those who were eliminated from the contest during this stage were:
- Penny Mordaunt
- Kemi Badenoch
- Tom Tugendhat
- Suella Braverman
- Jeremy Hunt
- Nadhim Zahawi
In stage two, the two MPs selected face a ballot of Conservative Party members, with each member voting only once.
Ballots were sent to members via post between August 1 and August 5. The vote closed at 5pm on Friday, September 2.
The candidate who receives the most votes will become the next prime minister.
When will Boris Johnson leave office?
The Queen will appoint the new prime minister from Scotland for the first time, the Palace confirmed on Wednesday,
Boris Johnson will be received at the monarch’s Balmoral Estate on Tuesday, September 6, as his final engagement as prime minister.
From Tuesday afternoon, it is expected that the new leader will begin to appoint their top government team.