Oklahoma Gov. Kevin Stitt has announced that Alan Armstrong, an energy executive, will fill the vacant Senate seat left by Markwayne Mullin until the end of the year.

Armstrong, 63, has never held public office and is the executive chairman of Williams Companies, an energy firm that specializes in natural gas.

Mullin’s seat was left open Monday night after he was confirmed to lead the Department of Homeland Security.

“Alan’s story, as you guys get to know him, reflects the very best of Oklahoma, our values, our work ethic and our pursuit of the American dream is the life well of the state of Oklahoma,” Stitt said at a press conference in Oklahoma Tuesday morning.

The governor claimed Armstrong is “thoroughly aligned with President [Donald] Trump on energy policy. Few people have done more to champion the ‘America First’ agenda to keep Oklahoma at the center of domestic production so that we can deliver clean, reliable, and affordable energy to American citizens.”

In his capacity as a businessman, Armstrong has dealt closely with the Trump administration, especially Secretary of Energy Chris Wright and Interior Secretary Doug Burgum, on American energy dominance through natural gas.

He is bringing his background in natural gas and energy to Washington and plans to focus on permitting reform.

“There’s a lot of things in terms of supporting Republican agenda, I think there’s a lot of important policy issues that stand before us, I’ll be in support of that. But I think the area I actually can bring the most expertise and leadership to is permitting reform,” Armstrong said.

Stitt consulted Senate leadership before making the appointment. According to Stitt, Majority Leader John Thune, R-S.D., requested someone who could work across the aisle to get permitting reform done. 

“We can’t have a country that picks and chooses,” Stitt said, describing the problem he sees with permitting in the United States. “When you do everything right and you get those permits, we can’t let a new administration come in and kill projects.”  

“I have every confidence that Alan will bring the same integrity,” Stitt continued. “Bring the same integrity as his work ethic and love for Oklahoma that he’s shown his entire career. He will fight for our values, defend our freedom, and champion policies that strengthen families, create jobs and secure America’s future,” Stitt said. 

Armstrong did admit he feels slightly unprepared for taking on this role unexpectedly.  

“I’m a little bit like I’m stepping off into the abyss with not exactly sure what I’m getting into, but I’m confident I got great team around me, great support around me, and I really do look forward to making a difference for the short time that I’m in the Senate,” Armstrong said.  

Since Mullin’s seat was up for reelection in November 2026, Armstrong will serve in the U.S. Senate until January 2027. Under Oklahoma law, he is required to sign an affidavit, upon being sworn in, that he will not run for election.

Armstrong will be sworn in at the Capitol Tuesday afternoon.