The 2026 United States Senate election in Oklahoma will be held on November 3, 2026, to elect a member of the U.S. Senate to represent the state of Oklahoma. Incumbent Senator Alan Armstrong, who was appointed after the resignation of former Senator Markwayne Mullin, cannot seek a full term due to his agreement when taking the seat. Mullin was first elected in a 2022 special election triggered by the impending resignation of Jim Inhofe. Mullin initially announced that he was planning to seek his first full term in office, but in March 2026, President Donald Trump announced that Mullin would be his next nominee for secretary of homeland security; Mullin subsequently resigned the seat to take that position. Primary elections will be held on June 16, 2026. Democrats have not won a U.S. Senate race in Oklahoma since 1990.
United States Senate elections in Oklahoma are scheduled to be held on November 3, 2026, to elect a member of the U.S. Senate to represent the state of Oklahoma. Primary elections are scheduled for June 16 with a potential runoff election set for August 25 if no candidate receives over 50 percent of the vote in June. The candidate filing deadline is April 3.
The seat was originally held by Jim Inhofe, who was last elected in 2020. Two years later, in 2022, then-Congressman Markwayne Mullin won a special election to finish Inhofe's term after Inhofe had announced his resignation at the end of the 117th Congress. After Donald Trump won the 2024 United States presidential election, Mullin was rumored as a contender for secretary of the interior. Mullin's resignation would have affected the gubernatorial election, as governor Kevin Stitt would have appointed a replacement who must sign a potentially unenforceable oath promising not to run for reelection in 2026. Mullin was ultimately not nominated as the secretary of interior. However, in March 2026, Mullin was named as Trump's pick to replace secretary of homeland security Kristi Noem and was confirmed on March 23, 2026.
Mullin was confirmed as the secretary of homeland security and resigned as senator on March 23, 2026. Governor Kevin Stitt was required to appoint a replacement within 30 days. He stated the appointee would serve the remainder of the current term until January 3, 2027, though state law provides that the appointment lasts only until the November election is certified by the Oklahoma State Election Board. The interim appointee must have been a registered Republican for the past five years, and they would have to sign an oath stating they will not run in the 2026 election. On March 24, 2026, Governor Stitt announced that oil and gas executive Alan Armstrong would replace Mullin, he was sworn in by Chuck Grassley later that day.
On March 5, 2026, Trump announced that Mullin would replace Homeland Security secretary Kristi Noem at the end of the month. Mullin was confirmed by the Senate on March 23, 2026. U.S. representative Kevin Hern has announced a run for the seat.
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