Oil and Gas Executive Alan Armstrong Sworn In as Oklahoma’s New U.S. Senator
Mullin resigned from the Senate earlier that day after being confirmed and sworn in as Secretary of the Department of Homeland Security in the Trump administration.
Tommy Flynn
WASHINGTON – Oil and gas executive Alan Armstrong was sworn in as Oklahoma’s newest Republican U.S. Senator on March 24, 2026, hours after Oklahoma Gov. Kevin Stitt appointed him to fill the vacancy created by Sen. Markwayne Mullin’s departure.
Mullin resigned from the Senate earlier that day after being confirmed and sworn in as Secretary of the Department of Homeland Security in the Trump administration.
Armstrong, the longtime Executive Chairman of Tulsa-based Williams Companies, will serve temporarily until a special election is held in November 2026 to choose a permanent successor for the remainder of the term. Under Oklahoma law, he signed a pledge not to run for the seat himself and will leave office in early 2027 once the elected senator is seated.
Gov. Stitt announced the appointment at a press conference in Oklahoma City on March 24, describing Armstrong as “a proud third-generation Oklahoman, staunch conservative, respected business leader, and a devoted family man with an inspiring American Dream story.”
Stitt added that Armstrong is “strongly aligned” with President Donald Trump on energy policy and will bring critical private-sector experience to the Senate at a time when advancing permitting reform and securing America’s energy future are top priorities. “He is entering the U.S. Senate at a critical time for advancing reforms to secure America’s energy future,” Stitt said. “I have no doubt that his perspective will be influential in moving the needle on permitting reform to unlock American competitiveness and energy affordability for generations to come.”
Armstrong has spent more than 40 years at Williams Companies, one of the nation’s largest natural gas infrastructure firms. He joined the company in 1986 as an engineer, advanced through leadership roles, and served as President and CEO from 2011 until transitioning to Executive Chairman in 2025. Under his leadership, Williams expanded its pipeline network and now transports approximately 30 percent of the natural gas consumed in the United States.
The appointment keeps the seat in Republican hands and maintains the GOP’s Senate majority. Armstrong participated in a ceremonial swearing-in at the U.S. Capitol shortly after the governor’s announcement.