The Report to the Commissioner of Baseball of an Independent Investigation into the Illegal Use of Steroids and Other Performance Enhancing Substances by Players in Major League Baseball, informally known as the Mitchell Report, is the result of former Democratic United States Senator from Maine George J. Mitchell's 20-month investigation into the use of anabolic steroids and human growth hormone (HGH) in Major League Baseball (MLB). The 409-page report, released on December 13, 2007, covers the history of the use of illegal performance-enhancing substances by players and the effectiveness of the MLB Joint Drug Prevention and Treatment Program. The report also advances certain recommendations regarding the handling of past illegal drug use and future prevention practices. In addition, the report names 89 MLB players who are alleged to have used steroids or other performance-enhancing drugs.

George John Mitchell Jr. is an American politician, diplomat, and lawyer. A leading member of the Democratic Party, he served as a United States senator from Maine from 1980 to 1995, and as Senate Majority Leader from 1989 to 1995. After retiring from the Senate, Mitchell played a leading role in negotiations for peace in Northern Ireland and the Middle East. He was appointed United States Special Envoy for Northern Ireland (1995–2001) by President Clinton and as United States Special Envoy for Middle East Peace (2009–2011) by President Barack Obama.