Matthew George Whitaker is an American lawyer, politician, and diplomat serving as the 26th United States ambassador to NATO since 2025 in the second administration of President Donald Trump. A member of the Republican Party, he previously served in Trump's first administration as acting United States attorney general from November 2018 to February 2019, following the resignation of Jeff Sessions. Whitaker had previously served as Chief of Staff for Sessions from October 2017 to November 2018.