Theodore Fulton Stevens (born November 18, 1923) is a former United States Senator from Alaska, serving from December 24, 1968, until January 3, 2009. Stevens was President pro tempore in the 108th and 109th Congresses from January 3, 2003, to January 3, 2007. Stevens is the longest-serving Republican senator in history (Strom Thurmond, who might otherwise have held this title, was a Democrat until 1964) and 7th longest-serving senator in history. Stevens was Alaska's senior senator all but 10 days of his tenure. Stevens was replaced as President pro tem by Robert Byrd assuming Byrd's previous honorary role of "President pro tempore emeritus." He is only the third Senator to hold the title of President pro tempore emeritus, having been preceded in this position by Byrd and Strom Thurmond.

Stevens served for six decades in the American public sector, beginning with his service in World War II. In the 1950s, he held senior positions in the Eisenhower Interior Department. He served continuously in the Senate since December 1968. He played key roles in legislation that shaped Alaska's economic and social development, including the Alaska Native Claims Settlement Act, the Trans-Alaska Pipeline Authorization Act, the Alaska National Interest Lands Conservation Act, and the Magnuson-Stevens Fishery Conservation and Management Act. He is also known for his sponsorship of the Amateur Sports Act of 1978, which resulted in the establishment of the United States Olympic Committee.

On July 29, 2008, Stevens was indicted by a federal grand jury on seven counts of failing to report gifts received from VECO Corporation and its CEO Bill Allen on his Senate financial disclosure forms, formally charged with violation of provisions of the Ethics in Government Act. Stevens pleaded not guilty and asserted his right to a speedy trial, which began on September 25 in Washington, DC, to have the opportunity to clear his name before the November election. On October 27, 2008, barely a week before the election, Stevens was found guilty on all seven counts. National Public Radio reported on April 1, 2009, that United States Attorney General Eric Holder, citing serious prosecutorial misconduct during the trial, decided to drop all charges against Stevens—an action that vacated his conviction.