Theodore Bevry Olson (September 11, 1940 – November 13, 2024) was an American lawyer who served as the 42nd solicitor general of the United States from 2001 to 2004 in the administration of President George W. Bush. He previously served as the Assistant Attorney General of the Office of Legal Counsel of the U.S. Department of Justice from 1981 to 1984 under President Ronald Reagan, and he was also a longtime partner at the law firm Gibson Dunn.

Olson was born on September 11, 1940, in Chicago, the son of Yvonne Lucy (née Bevry) and Lester W. Olson. He grew up in Mountain View, California, in the San Francisco Bay Area. After graduating from Los Altos High School in 1958, he studied communications and history at the University of the Pacific, where he was a charter member of the Phi Kappa Tau fraternity chapter. He graduated in 1962 with a Bachelor of Arts, cum laude. He then attended the UC Berkeley School of Law, where he was a member of the California Law Review and campaigned for Republican Senator Barry Goldwater for president in 1964. He graduated in 1965 with Order of the Coif membership.

In 1965, Olson joined the Los Angeles office of Gibson, Dunn & Crutcher as an associate. In 1972, he was named a partner. From 1981 to 1984, Olson served as an Assistant Attorney General (Office of Legal Counsel) in the Ronald Reagan administration. While serving in the Reagan administration, Olson was Legal Counsel to President Reagan during the Iran-Contra Affair's investigation phase. Olson was also the Assistant Attorney General for the Office of Legal Counsel when then-President Ronald Reagan ordered the Administrator of the EPA to withhold documents on the ground that they contained "enforcement sensitive information."

This led to an investigation by the U.S. House Judiciary Committee that later produced a report suggesting Olson had given false and misleading testimony before a House subcommittee during the investigation. The Judiciary Committee forwarded a copy of the report to the Attorney General, requesting the appointment of an independent counsel investigation. Olson argued that the Independent Counsel took executive powers away from the office of the President of the United States and created a hybrid "fourth branch" of government that was ultimately answerable to no one. He argued that the broad powers of the Independent Counsel could be easily abused or corrupted by partisanship. In the United States Supreme Court Case Morrison v. Olson, the Court disagreed with Olson and found in favor of the Plaintiff and independent counsel Alexia Morrison.

Olson returned to private law practice as a partner in the Washington, D.C., office of his firm, Gibson Dunn. A high-profile client of his in the 1980s was Jonathan Pollard, who had been convicted of selling government secrets to Israel. Olson handled the appeal to United States Court of Appeals for the D.C. Circuit. Olson argued the life sentence Pollard received was in violation of the plea bargain agreement, which had specifically excluded a life sentence. Olson also argued that the violation of the plea bargain was grounds for a mistrial. The Court of Appeals ruled (2‑1) that no grounds for mistrial existed. Olson argued a dozen cases before the Supreme Court prior to becoming Solicitor General. In one case, he argued against federal sentencing guidelines, and, in a case in New York state he defended a member of the press who had first leaked the Anita Hill story.

Olson successfully represented presidential candidate George W. Bush in the Supreme Court case Bush v. Gore, which effectively ended the recount of the contested 2000 U.S. presidential election. On December 11, 2000, Olson personally delivered the oral arguments before the Supreme Court on behalf of Bush.

Olson was nominated for the office of Solicitor General by President Bush on February 14, 2001. He was confirmed by the United States Senate on May 24, 2001, and took office on June 11, 2001. Olson was solicitor general during the 9/11 terrorist attacks, and his wife died on board American Airlines flight 77, which was crashed into the Pentagon. In 2002, Olson argued for the federal government in the Supreme Court case Christopher v. Harbury (536 U.S. 403), in which Supreme Court agreed with Olson's position in its unanimous opinion written by Justice Souter. Olson maintained that the government had an inherent right to lie: "There are lots of different situations where the government quite legitimately may have reasons to give false information out."

In July 2004, Olson retired as Solicitor General and returned to private practice at the Washington office of Gibson Dunn. In 2006, Olson represented a defendant journalist in the civil case filed by Wen Ho Lee and pursued the appeal to the Supreme Court. Lee sued the federal government to discover which public officials had named him as a suspect to journalists before he had been charged. Olson wrote a brief on behalf of one of the journalists involved in the case, saying that journalists should not have to identify confidential sources, even if subpoenaed by a court. In 2011, Olson represented the National Football League Players Association in the 2011 NFL lockout.