Mr Johnson will remain as Prime Minister until a replacement Tory party leader is appointed.
There are a string of candidates who are in the running for becoming the next prime minister.
Here’s everything you need to know about the leader’s potential replacements.
Who could replace Prime Minister Boris Johnson now that he has resigned?
There are several candidates who are believed to be potential replacements for Boris Johnson, now that the prime minister has decided to step down and resign from his role.
The former foreign secretary and ex-health secretary, Jeremy Hunt, was already a runner-up to Boris Johnson in the 2019 leadership bid.
He is already a favourite with bookmakers and had called on the prime minister to resign from his role.
Currently the chairman of the Commons Health Committee, he has been heavily involved with the government’s handling of the pandemic despite criticism of his abilities when he was health secretary.
Having resigned from his role on Tuesday, July 5, 2022, former health secretary Sajid Javid has already been in the running for becoming the Tory leader.
In 2019, he was among the final four candidates to replace Theresa May, but eventually dropped out and backed Boris Johnson.
The MP comes from humble beginnings as the son of a bus driver who moved to England from Pakistan in the 1960s. He has worked his way up in politics, having held roles in housing, business and culture before becoming chancellor, and later replacing Matt Hancock in the midst of the pandemic.
Like Sajid Javid, Rishi Sunak has also resigned from his role as chancellor after ‘concerns about leadership’.
The minister headed up the furlough scheme following thousands of Brits struggling amid the Covid outbreak in 2020, but faced major backlash for cutting the Universal Credit uptick the government introduced during the pandemic.
He has also been slated after disclosures about his wife’s non-dom status for tax purposes, and for his slow and concerning approach to the cost of living crisis, which has plunged people across the UK into poverty in 2022.
However, the former chancellor is still a firm favourite among bookies to replace Boris Johnson.
Former defence secretary Penny Mordaunt was fired by Boris Johnson when he became Prime Minister, but she is now a frontrunner for replacing the Conservative party leader.
She played a significant role in the Vote Leave Brexit campaign in 2016 and is also a Royal Navy reservist, along with being the current trade minister.
You may have also spotted her on Tom Daley’s diving TV show, Splash.
Having made it clear that he believes Boris Johnson should resign in January 2022, Tom Tugendhat gained popularity from the public for being outspoken about his thoughts on the Prime Minister’s leadership.
The chairman of the Foreign Affairs Committee was a Remainer in 2016 and, given his thoughts on the Tory leader and Brexit stance, previously stood little chance of replacing Johnson.
Foreign secretary Liz Truss is also in the running for becoming Prime Minister, but has made it clear she is “100% behind the PM”.
Her views are strongly aligned with that of her party, making her a popular candidate among them, including threats to tear up the Northern Ireland Protocol with the EU and insisting Russian forces must be driven from Ukraine.
In her role as foreign secretary, Truss has made a series of gaffes such as confusing the Baltic and Black sea, and mistaking the Greek foreign secretary with a Greek singer.
Despite backing Boris Johnson repeatedly, defence secretary Ben Wallace is also a frontrunner for the role of Prime Minister.
He is popular within the Tory party for his straight-talking and has consistently backed an increase in the UK’s defence spending.
He has been another key voice in the UK’s response to Russia’s brutal invasion of Ukraine.
Former education secretary Nadhim Zahawi was recently appointed the new chancellor, on Wednesday, July 6, 2022, replacing Rishi Sunak.
He rose to prominence as the vaccines minister during the pandemic and was praised for the speedy rollout of the Covid jab.
Having fled the regime of Saddam Hussein in Iraq, Zahawi moved to the UK when he was nine years old.