The United States House of Representatives Select Committee on Assassinations (HSCA) was established on September 15, 1976 by U.S. House Resolution 1540 to investigate the assassinations of John F. Kennedy and Martin Luther King Jr. in 1963 and 1968, respectively. The select committee was first formed by the 94th United States Congress, and expired at the end of the 95th Congress.

The HSCA completed its investigation in 1978 and issued its final report in 1979, which concluded that Kennedy “was probably assassinated as a result of a conspiracy.” In addition to acoustic analysis of a police channel dictabelt recording, the HSCA also commissioned numerous other scientific studies of assassination-related evidence that corroborate the Warren Commission's findings. However, the HSCA challenged the Warren Commission's conclusion that Lee Harvey Oswald was the only shooter, while stating that it was “unable to identify the other gunman or the extent of the conspiracy.” The HSCA likewise concluded, based on circumstantial evidence, that there was a “likelihood” King was also assassinated “as a result of a conspiracy.” The two-year inquiry cost $5.8 million. In December 1978, the HSCA recommended that the Department of Justice review its findings to decide if further investigation was merited.

The HSCA found that although the Commission and the different agencies and departments examining Kennedy's assassination performed in good faith and were thorough in their investigation of Oswald, they performed with “varying degrees of competency” and the search for possible conspiracy was inadequate. The HSCA determined, based on available evidence, that the probable conspiracy did not involve the governments of Cuba or the Soviet Union. The committee also stated that the conspiracy did not involve any organized crime group, anti-Castro group, nor the FBI, CIA, or Secret Service. The committee found that it could not exclude the possibility that individual members of the national syndicate of organized crime or anti-Castro Cubans were involved in a probable conspiracy to assassinate President Kennedy. However, some members of the committee would later state their personal belief that one of those groups was involved in the assassination, with Representative Floyd Fithian believing that the Kennedy assassination was orchestrated by members of organized crime.

In a memorandum written to the House Judiciary Committee in 1988 by Criminal Division Assistant Attorney General William F. Weld, the recommendations of the HSCA report were formally reviewed and a conclusion of active investigations was reported. In light of investigative reports from the FBI's Technical Services Division and the National Academy of Sciences Committee determining that “reliable acoustic data do not support a conclusion that there was a second gunman” in the Kennedy assassination, and that all investigative leads known to the Justice Department for both assassinations had been “exhaustively pursued”, the Department concluded “that no persuasive evidence can be identified to support the theory of a conspiracy in either the assassination of President Kennedy or the assassination of Dr. King.”

Several forces contributed to the formation of the HSCA. With the rapidly growing body of assassination conspiracy material, public trust in the findings of the Warren Commission report was declining. The Hart-Schweiker and Church Committee hearings had recently revealed CIA ties to other assassinations and assassination attempts and illegal actions from federal administration (FBI and IRS). The Church Commission also conducted an investigation into the assassination of John F. Kennedy in 1963, concluding that the federal agencies the FBI and the CIA had failed in their duties and responsibilities and that the investigation into the assassination had been deficient.

There was also significant public interest after a video segment of the Zapruder film was first shown on TV on March 6, 1975, during the ABC late-night television show Good Night America, after being stored by Life magazine out of view for almost twelve years. The footage showed the president's head recoiling violently backwards inside the presidential limousine during the fatal shooting as Lee Harvey Oswald was more than 80 yards behind. The public, having more and more difficulty accepting the conclusions of the Warren Commission report, led members of Congress to ask for new investigations into the assassination, within the framework of a new Commission of Inquiry.

In September 1976, the United States House of Representatives voted 280–65 to establish the Select Committee on Assassinations (HSCA) in order to investigate the assassinations of John F. Kennedy and Martin Luther King Jr.

The committee was both controversial and divided among itself. The first chairman, Thomas N. Downing of Virginia, retired in January 1977 and was replaced by Henry B. Gonzalez on February 2, 1977. Gonzalez and Chief Counsel Richard A. Sprague had irreconcilable disagreements over control of the committee, budget, and investigative techniques, ending with Gonzalez's resignation. Sprague also resigned, in part to increase the chances of Congress voting to reconstitute the HSCA for the new two-year congressional term. Sprague's like-minded deputy Robert K. Tanenbaum similarly resigned shortly thereafter. Louis Stokes replaced Gonzalez as chairman, and G. Robert Blakey was appointed as Chief Counsel and Staff Director to replace Sprague.