Alan Armstrong, a third-generation Oklahoman, business leader and former energy executive, was sworn in Tuesday as United States Senator from Oklahoma after being appointed by Governor Kevin Stitt to fill the remainder of the term vacated by former Senator Markwayne Mullin following his confirmation as Secretary of Homeland Security.
“I am honored that Governor Stitt has entrusted me with this responsibility and I’m grateful for the opportunity to serve the people of Oklahoma in the United States Senate,” Armstrong said. “I look forward to working with President Trump and Senate Republicans to strengthen our economy, unleash American energy, and continue to keep our nation safe.”
Background
Alan Armstrong was the Executive Chairman of the Board of Directors at Williams Companies, a leading provider of energy infrastructure in North America. Appointed to the role in July 2025, Armstrong transitioned from his long-standing position as president and CEO, a role he held since 2011.
Prior to being named CEO of Williams, Armstrong led the company’s North American midstream and olefins businesses through a period of growth and expansion as Senior Vice President – Midstream. He also served in a number of operational and commercial roles in various business units at Williams. Armstrong began his career at Williams nearly four decades ago as an engineer and steadily rose through the ranks, demonstrating a deep commitment to operational excellence, strategic growth and environmental stewardship.
Armstrong is the former Chair of the National Petroleum Council and is a founding member of Natural Allies for a Clean Energy Future. He serves as Chair of the Board of Trustees for the University of Oklahoma Foundation and is a board member for BOK Financial Corp. In addition, he is the former Chair of Junior Achievement USA. Armstrong earned his bachelor’s degree in civil engineering from the University of Oklahoma.
Speaker Hilbert Congratulates Alan Armstrong on Appointment to U.S. Senate, Highlights Oklahoma’s Responsible Vacancy Law:
Oklahoma House Speaker Kyle Hilbert, R-Bristow, today congratulates newly appointed Senator Alan Armstrong to temporarily serve in the United States Senate, noting that the appointment reflects the constitutional process established by the Oklahoma legislature in 2021.
The state’s current vacancy process was made possible through Senate Bill 959, authored by Speaker Hilbert and Senate President Pro Tempore Lonnie Paxton, R-Tuttle, which created a framework for Oklahoma governors to temporarily fill a U.S. Senate vacancy.
“Oklahoma once had a gap in our statutes that left the state without a clear process to temporarily fill a U.S. Senate vacancy,” Hilbert said. “In 2021, the Legislature acted to correct that oversight and ensure Oklahoma would always maintain full representation in Washington when a vacancy occurs.”
Senate Bill 959 aligned Oklahoma statute with the authority outlined in the Seventeenth Amendment to the United States Constitution, which allows state legislatures to empower governors to make temporary Senate appointments until voters can select a permanent replacement through an election.
Under Oklahoma law, any individual appointed to the Senate must have been a member of the same political party as their predecessor for the previous five years and must also sign a public oath with the Oklahoma Secretary of State affirming they will not seek the office when it next appears on the ballot. The provision ensures the people of Oklahoma ultimately choose their long-term senator.
While the legislation received little national attention at the time, it has now been utilized twice. In addition to enabling temporary appointments, SB 959 created a process for an “irrevocable resignation,” which was used by the late Senator Jim Inhofe to step down while allowing the seat to be filled during a regular election cycle.
“This law ensures Oklahoma maintains representation in the U.S. Senate while preserving the voters’ right to choose their long-term senator,” Hilbert said. “I look forward to working with newly appointed Senator Armstrong as he begins his journey to our nation’s capital.”
