The 2026 U.S. Senate election in Oklahoma, scheduled for November 3, 2026, will feature Republican Congressman Kevin Hern against Democratic nurse N'Kiyla Jasmine Thomas. The race was triggered by the resignation of Markwayne Mullin, who left the Senate on March 23, 2026, after being confirmed as Secretary of Homeland Security, prompting Governor Kevin Stitt to appoint oil and gas executive Alan S. Armstrong as interim senator. Armstrong, sworn in the next day, is prohibited from running for a full term and had to sign an oath forgoing candidacy. Hern won the Republican nomination from a crowded primary field (with a June 16 primary and potential August 25 runoff), while several prominent Republicans like Representatives Stephanie Bice, Josh Brecheen, and Tom Cole declined to enter the race. Democrats face a significant challenge, as they have not won a Senate seat in Oklahoma since 1990. The general election will decide who holds the seat for the next term, with the interim appointment lasting only until the election results are certified.