Royal Navy reservist Penny Mordaunt has become the UK’s first female Defence Secretary.
The appointment comes despite Mr Williamson's "strenuous" denial that he was responsible for disclosing information about the Government's controversial 5G deal with Huawei.
In a swift Cabinet reshuffle after Mr Williamson's sacking, Mrs May appointed Ms Mordaunt Defence Secretary, with former Prisons Minister Rory Stewart replacing Ms Mordaunt as the Minister for International Development.
Ms Mordaunt said it was a "privilege" to be working with the "best armed forces in the world".
Is Ms Mordaunt a likely choice to be the new Defence Secretary?
Ms Mordaunt is a prominent Leave campaigner, and last year there was speculation she might resign over Theresa May’s Withdrawal Agreement.
However, Ms Mordaunt did not and her public show of support for the Prime Minister seems to have paid dividends with a promotion from International Development Secretary that is likely to please Eurosceptics.
The 46-year-old retains the job of minister for women and equalities.
What is her background in politics?
Ms Mordaunt failed in her first attempt at the Portsmouth North seat in 2005, but overturned Labour’s majority to enter Parliament in 2010 and increased her share of the vote in each of the following polls.
She became a junior communities minister in 2014 and was then appointed the first female defence minister for the armed forces in UK history in 2015, and backed Andrea Leadsom in her unsuccessful bid to succeed Mr Cameron in 2016.
Ms Mordaunt first achieved ministerial rank under David Cameron between 2014 and 2016 and was appointed minister for disabled people when Theresa May took power in 2016.
Her appointment to International Development Secretary in 2017 was welcomed by aid charities, who said she would be able to draw on her experience working in hospitals and orphanages in Romania as a student after the 1989 revolution.
What did Ms Mordaunt do before politics?
Born in Torquay as one of twins, Ms Mordaunt moved with her family to Portsmouth at the age of two.
Her teacher mother died from breast cancer when she was 15.
Educated at a local comprehensive, she worked as a magician’s assistant before studying drama at the Victoryland Theatre School and philosophy at Reading University.
She was Conservative head of youth under Sir John Major and worked in William Hague’s press office during his leadership, as well as in the 2004 election campaign of former US president George W Bush.
She also made a career in communications, business and charity, becoming director of Diabetes UK.
Does she have links to the military?
The daughter of a paratrooper-turned-teacher, she is a Royal Navy reservist, serving as an acting sub-lieutenant of the Portsmouth-based HMS King Alfred.
She was also once accused of trivialising Parliament after admitting she had smuggled repeated mentions of the word “c***” into a Commons speech as part of a bet with fellow reservists.
Haven't I seen her somewhere away from politics?
The new Defence Secretary is probably best known outside of Westminster for donning her swimsuit in the ITV TV show Splash! in 2014, when she joined celebrities to be trained in diving by Olympian Tom Daley.