Names of a possible successor have been mooted but there is no clear-cut favourite.
Jeremy Hunt
Former foreign and health secretary Jeremy Hunt, 55, lost to Mr Johnson in the 2019 leadership contest, when he branded himself as the "serious" alternative.
Mr Hunt sent a thinly veiled campaign message for a new leadership bid ahead of the confidence vote, arguing that under Mr Johnson, "we are no longer trusted by the electorate" and "we are set to lose the next general election".
But the fluent Japanese speaker lacks Mr Johnson's charisma.
And in a sign of things to come if there is a new contest, his pre-pandemic record as health secretary was savaged by a Johnson ally before the vote.
Liz Truss
Foreign Secretary Liz Truss, 46, is a favourite of the Conservative rank and file for her outspokenness and willingness to go on the political attack.
But that has also stoked questions about her judgement, for instance when in February she encouraged Britons to go fight in Ukraine, and critics say her leadership posturing is too overt.
When she headed the Department for International Trade, some MPs dubbed it the "Department for Instagramming Truss" because of her prolific output on the social media site.
Rishi Sunak
The UK's first Hindu Chancellor of the Exchequer, 42, was until recently the bookmakers' favourite to succeed Johnson.
Like Ms Truss, he has a high profile on social media, and won plaudits for shoring up the economy during the pandemic.
But his refusal initially to authorise more support over a surging cost-of-living crisis, and questions over his family's huge wealth, have left Mr Sunak seriously weakened.
Sajid Javid
Health Secretary Sajid Javid, 52, is the son of a Pakistani immigrant bus driver who went on to become a high-flying banker and eventually Mr Johnson's finance minister before resigning in 2020.
Like Mr Sunak, he also faces questions about his personal wealth and tax affairs.
Priti Patel
Home Secretary Priti Patel, 50, is the most socially conservative of Mr Johnson's senior ministers, voting against same-sex marriage, and was a prominent Brexit supporter.
Ms Patel, born in London to a Ugandan-Indian family, has taken a tough line on immigration, while being confronted with record numbers of migrants crossing the Channel.
An avowed Thatcherite, she had to fend off claims she bullied civil servants.
Dominic Raab
Deputy prime minister and Justice Secretary Dominic Raab, 47, led the country when Mr Johnson was in intensive care in hospital with Covid-19 in 2020.
The former lawyer and karate black belt is seen as a reliable ally.
But his move to justice from the post of foreign secretary was seen as a demotion after he initially failed to cut short his holiday as Kabul fell to the Taliban in August.
Ben Wallace
The Defence Secretary, 52, has narrowly topped some recent polls of Tory grassroots' preferred next leader due to his role in the Ukraine crisis.
The former army officer and Johnson ally has downplayed wanting to lead the party, but is seen as a straight-talking and competent figure the Conservatives and country needs.
Nadhim Zahawi
The Education Secretary, 55, won widespread praise for overseeing Britain's pandemic vaccines roll-out.
His background, as a former refugee from Iraq who came to Britain as a child speaking no English, has also attracted praise in the media.
Prior to politics, he co-founded the prominent polling company YouGov.
But like Mr Sunak and Mr Javid, his private wealth has drawn adverse attention, including when he claimed parliamentary expenses for heating his horse stables.
Tom Tugendhat
A former army officer, Mr Tugendhat is a prominent backbencher from the so-called "One Nation" wing of the Tories who chairs parliament's influential Foreign Affairs Committee.
The 48-year-old has indicated he will stand in any leadership contest, but there is no love lost between him and Johnson loyalists.
A hawk on China, Mr Tugendhat has been critical of the government's botched handling of the troop withdrawal from Afghanistan.
Penny Mordaunt
Ms Mordaunt, 49, is the first woman to have been UK Defence Secretary and is currently a junior trade minister.
The Royal navy reservist is seen as likely to run but considered a long shot.
A strong Brexit supporter and key figure in the 2016 "Leave" campaign, she has been tipped as a potential unity candidate who could draw support from the Conservative party's warring factions.
