By Amy Harder and Peter Nicholas

WASHINGTON—President-elect Donald Trump on Wednesday chose Oklahoma Attorney General Scott Pruitt to lead the Environmental Protection Agency, according to a transition official, turning to a climate-change skeptic and sharp critic of the agency to take its helm.

As the chief legal officer of a major oil and natural-gas producing state, Mr. Pruitt, a Republican, has led legal fights against some of President Barack Obama’s most significant environmental rules, and one of his major roles as EPA administrator would likely be to try to roll back those regulations.

That prospect cheered some industry leaders—many of whom have been frustrated as the Obama administration unveiled far-reaching environmental rules as part of the president’s goal of fighting climate change—while drawing objections from environmentalists concerned over Mr. Pruitt’s questioning of climate change.

Harold Hamm, a top energy adviser to Mr. Trump and an ally of Mr. Pruitt’s, said Mr. Pruitt would take a different approach to the agency.

“He understands the regulatory stranglehold that the EPA has had on industry during the Obama administration,” said Mr. Hamm, founder and CEO of Continental Resources, which is based in Oklahoma City. “I believe that he will work to unleash prosperity in America through the proper use of regulations and adhering to the rule of law.”

Mr. Pruitt has touted his leadership role in fighting the EPA rule that cut power-plant carbon emissions, called the Clean Power Plan, as well as an EPA measure that put more bodies of water under federal jurisdiction. Both rules have been temporarily blocked by federal courts as litigation proceeds.

In choosing a legal official to head his EPA, Mr. Trump could be signaling that legal action will be central to carrying out his campaign promises to repeal a host of rules related to climate change and other environmental issues.

“We’re very accustomed to the naysayers and the critics,” senior Trump adviser Kellyanne Conway said when asked by reporters about criticism of Mr. Pruitt’s selection. “Attorney General Pruitt has great qualifications and a good record as AG of Oklahoma and there were a number of qualified candidates for that particular position that the president-elect interviewed. We look forward to the confirmation hearings.”

The selection of Mr. Pruitt reflects a request by some on Mr. Trump’s transition team that his cabinet—heavy on political allies and wealthy business leaders—should also include state officials and others not closely associated with the president-elect, according to two transition officials.

Mr. Pruitt has been a close ally of the oil and natural-gas industry, whose influence in Oklahoma rivals even its clout in Texas. He has pushed back against a group of Democratic attorneys general who are investigating Exxon Mobil Corp.’s handling of climate-change science in recent decades.

Mr. Pruitt has also indicated he questions the scientific consensus that human activity is helping raise the Earth’s temperature, though he has been less outspoken about it than some other candidates Mr. Trump was considering to head the EPA.

“Scientists continue to disagree about the degree and extent of global warming and its connection to the actions of mankind,” Mr. Pruitt said in an op-ed that he and Alabama Attorney General Luther Strange wrote in May for the Tulsa World. “That debate should be encouraged—in classrooms, public forums, and the halls of Congress.”

Groups representing U.S. farmers hope Mr. Pruitt will roll back Obama policies they view as burdensome, such as the rule putting more waterways and wetlands under federal protection. Farmers feared the rule, which Mr. Pruitt challenged as Oklahoma attorney general, would give the EPA oversight over their ditches and ponds and restrict crop production and land maintenance.

“He should be suited to take on these kinds of abuses and overreaching from the agency, to put the agency back on track,” said Ellen Steen, general counsel at the American Farm Bureau Federation.

Ms. Steen said the Farm Bureau, which has challenged the EPA water rule in court, hopes Mr. Pruitt will rescind the regulation.

Energy groups welcomed the selection of Mr. Pruitt, noting his industry-friendly record as a politician from an oil-and-gas-producing state. “We expect that he will consider all of the reliable available data before developing and implementing any new regulation impacting our industry,” the International Association of Drilling Contractors said.

But environmentalists were dismayed at the notion of placing someone at the head of the environmental agency who questions the scientific consensus on climate change.

“Americans want to transition to clean energy to protect our air, our water and our climate,” said climate activist Tom Steyer. “But rather than respecting the will of the people, Trump has chosen a nominee for Environmental Protection Agency Administrator who has a record of putting corporate polluters’ profits ahead of our health.”

Environmentalists urged the Senate to reject his nomination, although that would be an uphill climb as the chamber is controlled by Republicans. Sen. Charles Schumer (D., N.Y.), the incoming Senate Democratic leader, said Mr. Pruitt would face tough questions during his confirmation.

“Attorney General Pruitt’s reluctance to accept the facts or science on climate change couldn’t make him any more out of touch with the American people—and with reality,” Mr. Schumer said.

While Mr. Trump can’t generally repeal Mr. Obama’s rules unilaterally on his first day in office, he and his new EPA administrator, with the help of a GOP-controlled Congress, have a handful of ways to curtail the agency’s work. They can restrict EPA funding on particular issues, pass laws nullifying individual regulations, and opt not to defend rules that face court challenges, including the Clean Power Plan and the water rule.

The fate of the Clean Power Plan is currently in the hands of a federal appeals court in Washington, which is expected to rule in the coming months, possibly before Inauguration Day on Jan. 20.