Markwayne Mullin is an American businessman and Republican politician who represented Oklahoma in the U.S. House from 2013 to 2023 and in the Senate from 2023 until March 2026, when he became the ninth secretary of the Department of Homeland Security. He is an enrolled citizen of the Cherokee Nation.

Born in Tulsa in 1977, Mullin took over his family's company, Mullin Plumbing, after his father fell ill and grew it into a large regional service business before selling his companies in 2021. He also fought briefly as a professional mixed martial artist and works as a cow-calf rancher. He won Oklahoma's 2nd congressional district in 2012 and the 2022 special election to succeed Senator Jim Inhofe. In the Senate he sat on the Armed Services Committee, including its Emerging Threats and Capabilities Subcommittee, as well as the Environment and Public Works and Indian Affairs committees.

On March 5, 2026, President Donald Trump fired Kristi Noem and nominated Mullin to replace her. At his confirmation hearing before the Senate Homeland Security and Governmental Affairs Committee, chairman Rand Paul questioned his character; the committee advanced the nomination 8–7, the Senate confirmed him 54–45 on March 23, and he was sworn in the next day. As secretary he has led the administration's immigration enforcement, defending Immigration and Customs Enforcement after an October 2026 shooting during an arrest in New York and blaming sanctuary-city policies.

His connection to UAP is slight. His Armed Services subcommittee held the Senate's April 2023 open hearing with AARO director Sean Kirkpatrick, but the transcript lists only Senators Kirsten Gillibrand, Jacky Rosen and Joni Ernst as members present, and Mullin is not known to have sponsored UAP legislation or spoken at length on the subject. The department he now leads joined the FBI, FAA and Pentagon in December 2024 in reporting that a review of more than 5,000 New Jersey drone sightings found nothing anomalous, an assessment issued before his tenure. His significance in the UAP field therefore lies in office rather than record: he now heads a department whose role in assessing drone reports over American communities has become part of the wider argument about unidentified objects in domestic airspace.