Sunak, who is expected to be officially appointed by King Charles on Tuesday, will replace Liz Truss, the shortest-serving prime minister in British history.
In his first speech as Conservative Party leader, Sunak said Britain was facing "a profound economic challenge.”
He added: “We need stability and unity, and I will make it my utmost priority to bring our party and our country together.”
He paid tribute to Truss "for her dedicated public service to the country," saying that "she has led with dignity and grace through a time of great change.”
Sunak pledged to serve his country "with integrity and humility."
"I will work day in, day out to deliver for the British people,” he promised.
Once in office, Sunak will become the country's first prime minister of Indian origin, the Reuters news agency reported.
Sunak graduated from Oxford University and then studied at Stanford University in the United States, where he met his wife Akshata Murthy, whose father is Indian billionaire N. R. Narayana Murthy, founder of outsourcing giant Infosys, according to Reuters.
Sunak’s grandparents were born in India and his parents emigrated to Britain from East Africa in the 1960s, US broadcaster CNN reported.
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Source: PAP, Reuters, CNN