The Taliban's governing council chose Mullah Fazlullah, the head of a militant faction in the northwestern Swat Valley, after six days of deliberations, Taliban officials told reporters. Mullah Fazlullah is said to be responsible for last year's attack on Malala Yousafzai, the teenage Pakistani education activist.
Mr. Fazlullah is best known for ordering public beatings, executions and beheadings, and delivering thunderous radio broadcasts - in which he denounced polio vaccinations, among other topics - that earned him the nickname "Mullah Radio" in some circles, reports The New York Times.
Celebratory gunfire erupted in North Waziristan, the tribal district that is Pakistan's main militant hub, after Mr. Fazlullah's accession was announced. But the news was likely to be received with less enthusiasm by Prime Minister Nawaz Sharif's government.
Furious officials criticized the United States' killing of the previous Taliban leader, Hakimullah Mehsud, in a drone strike last Friday, claiming that the Mr. Mehsud had been on the verge of starting peace talks with the government.
Pakistan ministers slam US for the drone attack that killed Mehsud
But few believed those talks had much chance of success, and Mr. Fazlullah, who reneged on a previous peace deal in 2009, offers even dimmer hopes. On Thursday, his spokesman, Shahidullah Shahid, said there would be "no more talks as Mullah Fazlullah is already against negotiations."
Instead, Mr. Shahid said, the Taliban were planning retaliatory attacks against the federal government in Punjab, Pakistan's most populous province. Mr. Sharif "bargained and sold out Hakimullah to the Americans," he said.
For the Pakistani military, Mr. Fazlullah is a cherished enemy. He escaped the army's toughest anti-Taliban offensive of recent years in 2009 when, as thousands of soldiers swept through Swat, after the collapse of a peace deal, he fled across the border into Afghanistan.
Since then he is believed to have been hiding in Kunar and Nuristan Provinces in eastern Afghanistan, using the mountains as a base to stage attacks inside Pakistan, including the attack on Ms. Yousafzai, who was shot in the head by a Taliban gunman in October 2012.
Mr. Fazlullah claimed a major military target this year when his fighters killed a two-star army general in Dir district, near the Afghan border, in September.
Mr. Fazlullah was not the favored candidate to succeed Mr. Mehsud because he did not hail from the Mehsud tribe, which has dominated the leadership of the Pakistani Taliban since the group was founded in 2007.
The ranks of the Mehsud leadership, however, have been thinned by the C.I.A. drone campaign. Strikes in North and South Waziristan killed both Hakimullah and his predecessor, Baitullah Mehsud, who died in 2009.
A former security official, speaking on the condition of anonymity, said Mr. Fazlullah had been chosen to avert a rift between rival Mehsud factions inside the Taliban.
The Taliban also appointed Khalid Haqqani, a little-known commander from a rural district near Peshawar, as the deputy commander, effectively signaling a shift in the Taliban leadership from the tribal belt to neighboring Khyber-Pakhtunkhwa Province.
"This changes the entire equation," said one senior government official in Peshawar.
Mr. Fazlullah, believed to be in his late 30s, offers the Taliban the opportunity of a possible new direction, led by a figure with a reputation for being charismatic, ruthless and publicity-savvy.
From a poor family, Mr. Fazlullah started his adult life as the operator of a chairlift that spanned the river Swat. He rose to public prominence in 2007 by riding on a white horse into Swat, a picturesque area once popular with honeymooning couples.
He set up a pirate radio station that broadcast jihadist propaganda across the valley, at one point urging women not to sleep with their husbands if they refused to join his jihad. Soon afterward, armed fighters displaced the civil government, instituting an authoritarian and often cruel rule that mandated public floggings, executions and the closing of girls' schools.
The provincial and federal governments struggled to respond to Mr. Fazlullah's swagger, signing two peace deals with his father-in-law, Sufi Muhammad, in a bid to re-establish calm in the valley. But those compromises quickly foundered - there was public outrage across Pakistan over a video that showed Taliban fighters flogging a teenage girl in Swat - and by the summer of 2009, the army had moved in.
Since then, the Swat Taliban have been reduced to hit-and-run attacks, while the army has been accused by human rights groups of carrying out summary executions of people suspected of being militants.
The Taliban's most infamous operation of recent years was the attack on Ms. Yousafzai, then 15. At the time, Mr. Fazlullah's spokesman said she had been shot for her advocacy, and vowed to shoot her again if she returned to Swat. Ms. Yousafzai was flown to Britain for emergency treatment, where she recovered from her injuries, and has gone on to become a global celebrity.
Mr. Fazlullah's rise now presents potential difficulties for Imran Khan, the former cricket star whose party governs Khyber-Pakhtunkhwa Province, of which Swat is one district. Mr. Khan has threatened to block NATO military supply lines into Afghanistan after Nov. 20 if the United States does not halt drone attacks in the tribal belt.
But Mr. Khan's aggressive anti-American stance could be complicated by a new wave of Taliban violence - particularly if it is engineered by a Taliban leader who hails from the province that Mr. Khan controls.
(With agency inputs)