The ex-equalities minister, who is on the right of the party, is standing on an anti-woke and small government platform.
She told the crowd in Westminster that there “are always tough choices in life and in politics; no free lunches, no tax cuts without limits on Government spending, no stronger defence without a slimmer state.”
The 42-year-old MP for Saffron Walden has the declared support of more than a dozen Tory colleagues, including Michael Gove who was sacked as a cabinet minister by Boris Johnson shortly before he was forced to resign.
What is her political background?
Born in Wimbledon, Ms Badenoch lived in the US and Nigeria as a child before returning to the UK aged 16.
She has talked about working in McDonald’s while studying for her A-levels in Morden.
After graduating from the University of Sussex with a masters degree in Computer Systems Engineering, she worked for companies including the Royal Bank of Scotland, private bank coutts and the Spectator magazine.
She joined the Conservative party in 2005, aged 25.
Five years later she stood as the Tory candidate in Dulwich and West Norwood, coming third in the vote won by Labour’s Tessa Jowell.
In 2012, she stood for the Conservatives in the London Assembly election.
The party won just three seats and Ms Badenoch was placed fifth on the London-wide list, behind Suella Braverman in fourth, meaning she was not elected.
At the 2015 general election, City Hall Tory Victoria Borwick was elected as an MP and resigned her seat on the London Assembly.
Ms Braverman, who is contesting the Tory leadership alongside Ms Badenoch, also won a seat in the House of Commons that same year and declined to fill the vacancy.
Ms Badenoch was therefore called on to take up the seat in City Hall in September 2015. She went on to retain it at the 2016 London Assembly elections.
She was the London Tory spokesman for the Economy and also sat on the Transport Committee and Policing and Crime Committee.
In the 2017 election she stood in the safe Conservative seat of Saffron Walden in Essex and was elected to Parliament.
She has described herself as an example of the “British dream”, an “immigrant who came to the UK aged 16 and who became a parliamentarian” in one generation.
Winston Churchill and Margaret Thatcher have been cited among her personal heroes.
What government role does she currently hold?
Ms Badenoch is one of the few Tory leadership hopefuls who has never held a cabinet level job.
She resigned her a roles as equalities minister and minister in the Department for Levelling Up on July 6, saying she had lost faith in Boris Johnson as prime minister.
Previously, she was the exchequer secretary to the Treasury from February 2020 to September 2021 and a junior minister at the Department for Education from July 2019 to February 2020.
What was her position on Brexit?
Ms Badenoch was a supporter of Brexit.
In a rousing maiden speech in Parliament she described the referendum as “the greatest ever vote of confidence in the project of the United Kingdom.”
Her banker husband, Hamish, a former Merton Conservative councillor, was a staunch Remainer.
“We have had robust arguments but respect each other’s view,” Ms Badenoch told the Independent in 2017.
Ms Badenoch was criticised for publicly shaming journalist Nadine White last year.
The HuffPost reporter had asked the then equalities minister’s office about suggestions Ms Badenoch had refused to participate in a video featuring Black cross-party politicians seeking to encourage the take up of the Covid-19 vaccination.
Screenshots of Ms White’s two emails were shared on twitter by Ms Badenoch who branded them “creepy and bizarre”.
Labour called for an investigation and Ms White said the MP’s actions set a dangerous precedent, threatening the role of a free press.
Ms Badenoch has admitted “hacking” Harriet Harman’s website in 2008 as part of a “foolish prank”.
She had guessed the Labour MP’s password and then posted a hoax blogpost claiming that the then minister for women and equality was supporting Boris Johnson in the London elections.
In 2018, she told Core Politics: “About 10 years ago I hacked into… a Labour MP’s website and I changed all the stuff in there to say nice things about Tories.”