Updated 1628 GMT (0028 HKT) October 25, 2022
Sunak is the first Hindu and the first person of color to lead the UK. At the age of 42, he is also the youngest person to take the office in more than 200 years.
The contest was staged after Truss quit as prime minister following a disastrous six-week term.
Sunak was first elected to Parliament in 2015, and he spent two years on the backbenches when Brexit dominated the political agenda. He subsequently became a junior minister in Theresa May's government.
It was Boris Johnson who gave Sunak his first major government role when he first appointed him as the chief secretary to the Treasury in 2019. Johnson also promoted Sunak to chancellor in 2020.