Britain’s Conservative Party announced on Monday, September 6, 2022, that its members had chosen Liz Truss to replace Boris Johnson as leader, turning to a hawkish diplomat, party stalwart and free-market champion to govern a country facing the gravest economic crisis in a generation.

Ms. Truss, 47, prevailed over Rishi Sunak, a former chancellor of the Exchequer, whose resignation in July set in motion Mr. Johnson’s messy ouster. Her victory, by a margin of 57.4 percent to 42.6 percent, was widely expected in recent weeks after she took a commanding lead in the polls.

It makes her Britain’s fourth prime minister in six years and third female leader, after Margaret Thatcher and Theresa May. Like them, she will be greeted by a fearsome array of problems.