Kemi Badenoch has promised to "renew" the Conservatives after being elected party leader, defeating fellow right winger Robert Jenrick.
She takes over from Rishi Sunak, who led the Conservatives to their worst ever election defeat in July.
In her victory speech, she told party members it is "time to get down to business" and "time to renew".
Badenoch, who was raised in Nigeria, is the first black woman to lead a major political party in the UK.