LONDON—Sadiq Khan, the son of Pakistani immigrants to the U.K., became the capital’s next mayor, in a win that marked a bright spot for the main opposition Labour Party after it suffered losses in other local elections.
Mr. Khan, who became the city’s first Muslim mayor, won by a wide margin, receiving more than 1.3 million votes, while Conservative candidate Zac Goldsmith received 994,614 votes, when counting second-choice...