The F.B.I. is an American police television series created by Quinn Martin and Philip Saltzman for ABC and distributed by Warner Bros. Television Distribution, with sponsorship from the Ford Motor Company, Alcoa and by American Tobacco Company, and, premiered in 1965 until its end in 1974. Starring Efrem Zimbalist, Jr., Philip Abbott and William Reynolds, the series, consisted of nine seasons and 241 episodes, chronicles a group of FBI agents trying to defend the US Government from unidentifed threats.

Produced by Quinn Martin and based in part on concepts from the 1959 Warner Bros. theatrical film The FBI Story, the series was based on actual FBI cases, with fictitious main characters carrying the stories. Efrem Zimbalist, Jr. played Inspector Lewis Erskine, a widower whose wife had been killed in an ambush meant for him. Philip Abbott played Arthur Ward, assistant director to FBI Director J. Edgar Hoover. Although Hoover served as series consultant until his death in 1972, he was never seen in the series.

Stephen Brooks played Inspector Erskine's assistant, Special Agent Jim Rhodes, for the first two seasons. Lynn Loring played Inspector Erskine's daughter and Rhodes' love interest, Barbara, in the first few episodes of the show. Although the couple was soon engaged on the show, that romantic angle was soon dropped.

In 1967, Brooks was replaced by veteran actor William Reynolds, who played Special Agent Tom Colby until 1973. The series would enjoy its highest ratings during this time, peaking at No. 10 in the 1970–1971 season. For the final season, Shelly Novack played Special Agent Chris Daniels.

Some episodes ended with a "most wanted" segment hosted by Zimbalist, noting the FBI's most wanted criminals of the day, decades before the Fox Network aired America's Most Wanted. The most famous instance was in the April 21, 1968 episode, when Zimbalist asked for information about fugitive James Earl Ray, who was being hunted for the assassination of Dr. Martin Luther King, Jr.

The series aired on ABC at 8 p.m. Sunday from 1965 to 1973, when it was moved up to 7:30 p.m. for the final season. The series was a co-production of Quinn Martin Productions and Warner Bros. Television, as Warner Bros. held the television and theatrical rights to any project based on The FBI Story. It was the longest-running of all of Quinn Martin's television series, airing nine seasons.

An updated and revamped version of the series, Today's FBI, executive produced by David Gerber for Columbia Pictures Television, aired on ABC from October 1981 through April 1982 in the same Sunday 8 p.m. time slot as its predecessor. A remake of the original series, produced by Ron Howard's Imagine Entertainment for Fox, was set for air in Fall 2008; but did not air.

Warner Bros. (under the Warner Home Video label) has released all nine seasons of The F.B.I. on DVD in region 1 via their Warner Archive Collection. These are Manufacture-on-Demand (MOD) releases and are available through Warner's online store and Amazon.com.^{[2][3][4][5][6][7]} The ninth and final season was released on September 23, 2014.^[8]