There are just two Conservative MPs in the running to be the leader of the Tory party after former Prime Minister Boris Johnson withdrew from the race.
Despite not being as well-known a name as some of the candidates, Ms Mordaunt was previously deemed one of the favourites with bookies when Boris Johnson stepped down, and was described as the "dark horse" of the contest.
Announcing her leadership bid, the Hampshire MP tweeted: "People deserve a leader that understands the life they lead. "And that is why I’m running to be Prime Minister."
Here is everything you need to know about the woman who could be our next prime minister:
Who is Penny Mordaunt?
Ms Mordaunt has been MP for Portsmouth North since 2010.
The 49-year-old made waves in 2019 as the UK’s first female defence secretary before being fired by Mr Johnson after just three months when he became prime minister.
She was eventually brought back into government and is now a trade minister after moving on from being paymaster general.
Ms Mordaunt previously served in David Cameron's government as a Parliamentary under-secretary and as international development secretary under Mrs May.
While Tory MPs and ministers publicly backed Mr Johnson in the confidence vote in June, Ms Mordaunt said she would be in her constituency attending a D-Day commemoration service.
Brexit support and Royal Navy career
The MP's other job as a member of the Royal Navy Reserves means she is likely to be popular among Tory voters.
She played a prominent role in the Leave campaign in the 2016 Brexit referendum, and has previously reportedly enjoyed the backing of Dame Andrea Leadsom among others.
Ms Mordaunt was previously married to Paul Murray, who she met while they were mature students at Reading University. They divorced in 2000.
She appeared on the Tom Daley-fronted reality TV diving show Splash in 2014.
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