Rishi Sunak will be Britain’s next prime minister after his last remaining rival Penny Mordaunt withdrew from the race.
Mr. Sunak was elected Conservative Party leader after winning the backing of a majority of Tory MPs.
He was the only candidate left standing after Ms. Mordaunt pulled out moments before the deadline for nominations.
Former prime minister Boris Johnson called off his comeback bid on Sunday.
Mr. Sunak, 42, will be appointed prime minister by King Charles III after Liz Truss formally tenders her resignation.
He will be Britain’s first Hindu prime minister, and the youngest in more than 200 years.
“This decision is a historic one and shows, once again, the diversity and talent of our party. Rishi has my full support,” Ms. Mordaunt said as she conceded defeat.
Party rulemaker Graham Brady said only one valid nomination, for Mr. Sunak, was received before the deadline.
He did not reveal whether Ms. Mordaunt would have had the 100 nominations from MPs needed to force a ballot.
Her withdrawal means the leadership question will not be put to the grassroots Tory membership.
Members chose Ms. Truss over Mr. Sunak in the summer contest to succeed Mr. Johnson, but her premiership imploded in 45 days after a botched mini-budget.
The race to replace Ms. Truss was compressed into a matter of days so that the new prime minister could quickly take charge of Britain’s economic crisis.