ROME — An anti-establishment newcomer, capitalizing on anger over political corruption and deteriorating city services, easily won Rome’s mayoral runoff on Sunday to become the first woman to lead the Italian capital.

With more than 80 percent of the ballots counted, Virginia Raggi of the Five Star Movement led by a 2-to-1 ratio. Her rival, Roberto Giachetti of the Democratic Party, who was backed by Prime Minister Matteo Renzi, conceded defeat less than an hour after polls closed.

Mr. Giachetti said he had called Ms. Raggi to wish her luck.

Dozens of people, including local politicians from the governing Democratic Party, right-wing parties and other political forces, have been implicated in corruption probes of city contracts.

While Rome’s established parties struggled, municipal services, especially strike-plagued mass transit, street repairs and trash collection, deteriorated to the exasperation of residents.