The MP was given the boost to one of the four great offices of state after impressing in her brief as International Trade Secretary. Responsible for signing post-Brexit free trade deals, she successfully brokered agreements with 96 countries around the world.
Her success made her a firm favourite among Tory grassroots, regularly topping polls as Conservative members’ favourite Cabinet minister.
It will be her fifth role in the Cabinet having become a regular face at the top table in recent years.
She will be the first female Conservative to ever hold the Foreign Secretary post.
Labour’s Margaret Beckett is the only other female to have held the role.
Ms Truss will also retain the role of minister for women and equalities, a position she was appointed to in September 2019.
The MP for South West Norfolk replaces Dominic Raab.
Mr Raab faced calls to resign since he went on holiday in Crete as the Taliban advanced on the Afghan capital, Kabul.
While Mr Johnson stood by him at the time, he was today demoted to Justice Secretary.
To soften the blow, Mr Raab was also appointed deputy prime minister, a role he played in all but name when he stepped in to lead Government when Mr Johnson was fighting for his life in hospital with Covid last year.
He was given the extra official title after a row behind closed doors over being sacked from the Foreign Secretary role.
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Taking over, Ms Truss will be responsible for forging a new role for the UK post-Brexit on the world stage.
She was a vocal Remainer during the EU referendum but her embrace of new opportunities outside the bloc has impressed Mr Johnson.
She said on Tuesday that British firms must do more to take advantage of new export routes opened up by Brexit.
“The path to economic revival does not lie in retreating and retrenching but in free trade and free enterprise,” she said.
Ms Truss has taken a hard line on dealing with Beijing in the past, calling on the West to “get tough with China”.
Anne Marie Trevelyan, Berwick-upon-Tweed MP, will take over as International Trade Secretary.
Since January she has served as a business minister but previously held the role of Secretary of State for International Development.