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...