We will soon see how she tackles political storms, international crises and life as the most senior figure in the UK on the public stage.
By modern standards, she is one of our more private MPs but her record gives us a hint of how she may lead the country.
Here is what we know about the new Conservative leader.
1. She’s not afraid to use shock tactics on the Tory grassroots
Back in 2002, the future Home Secretary startled her conference audience with her call for dramatic change in the party.
She said: “Yes, we’ve made progress, but let’s not kid ourselves. There’s a way to go before we can return to government.
“There’s a lot we need to do in this party of ours. Our base is too narrow and so, occasionally, are our sympathies.
“You know what some people call us: the nasty party.”
The party would go on to lose the 2005 election but David Cameron emerged as a champion of modernisation. The phrase “the nasty party” is now regularly used to attack the Conservatives.
2. Her life has not been easy
A Guardian profile described how this daughter of a vicar experienced family tragedies: “Her father was killed in a car crash shortly after she graduated, and her mother, who had multiple sclerosis, died the year after. Then came the bitter discovery that the Mays could not have children.”
3. She has changed her mind on gay rights
Mrs May opposed the repeal of Section 28 – which stopped councils “promoting” homosexuality in 2000 and voted against gay adoption in 2002.
But in 2010 she said she had “changed my mind” on adoption and in 2012 she announced her support for gay marriage.
4. She can take a controversial stand on civil liberties
Mrs May used her 2014 conference speech to say that she would go after all extremism, not just violent forms.
She said: “You don’t just get the freedom to live how you choose to live. You have to respect other people’s right to do so too.”
Staying on this theme, she said: “There will, I know, be some who say that what I describe as extremism is merely social conservatism. But if others described a woman’s intellect as ‘deficient’, denounced people on the basis of their religious beliefs, or rejected the democratic process, we would quite rightly condemn their bigotry.”
5. She is prepared to clash with senior Tories
Mrs May refused to allow water cannons to be used on the streets of London, even though then-Mayor of London Boris Johnson had authorised the purchase of three of these vehicles from Germany.
Far from hoping this episode would be forgotten, Mrs May used it last month to make a public dig at Mr Johnson and his negotiating skills, saying: “I seem to remember last time he did a deal with the Germans, he came back with three nearly-new water cannon.”
She also rowed with Michael Gove in 2014 when sources close to him said the Home Office had failed to “drain the swamp” of extremism.
6. She has demonstrated it is possible to live on the political frontline with diabetes
Mrs May has described living with type one diabetes.
She said: “I don’t inject insulin at the table, but I’m quite open about it. For example, I was at a dinner last night and needed to inject and so I just said to people: ‘You do start eating, I’ve got to go and do my insulin’. It’s better to be open like that.”
She added: “I would like the message to get across that it doesn’t change what you can do.”
7. She is willing to challenge powerful bodies
In 2014 she stood up at the Police Federation conference and demanded the organisation change, pointing out that “only 42% of black people from a Caribbean background trust the police”.
In an uncompromising speech she said: “Federation staff have been forced out and there have been allegations of bullying and victimisation. Instead of embracing the need for reform, some members of the Fed seems to have reverted to the worst kinds of behaviour…”