The boycott of the 1984 Summer Olympics in Los Angeles followed four years after the American-led boycott of the 1980 Summer Olympics in Moscow. The boycott involved nineteen countries: fifteen from the Eastern Bloc led by the Soviet Union, which initiated the boycott on May 8, 1984; and four non‑aligned countries which boycotted on their own initiatives. The boycotting countries organized alternative sporting events which functioned as a replacement for the Olympics in everything but name, called the Friendship Games, which were held in various Eastern Bloc countries from July to September of 1984. Although the boycott affected Olympic events that were normally dominated by the absent countries, 140 nations still took part in the Los Angeles Games, which was a record at the time.

Since the announcement by U.S. President Carter of the boycott of the Olympic Games in Moscow in 1980, there was fear from United States officials that a reciprocal boycott could occur during the 1984 Games, scheduled for Los Angeles. The Soviets for their part gave sparsely few indications that this would happen, and indeed, from formalized talks which occurred over the course of three years, indicators seemed to point towards Soviet participation. Only in the last year before the Games began did a sense of non-participation come about.

During that final year, the loss of Korean Air Lines Flight 007 and the subsequent vitriol directed at the Soviets by various activist groups which formed in the aftermath of the flight's destruction seriously hampered relations between the two committees tasked with coordinating Soviet attendance, the Los Angeles Olympic Organizing Committee (LAOOC) and the Soviet National Olympic Committee (Soviet NOC). Their faltering relations did not improve with the accession of Konstantin Chernenko to the post of General Secretary of the Soviet Union in February 1984. Chernenko was a close acolyte of Leonid Brezhnev and therefore predisposed to avoiding Los Angeles due to the 1980 boycott. American reticence in dealing with anti-Soviet activists coupled with American mishandling of the Soviets' Olympic attaché, incentivized the Soviets enough in their view to justify boycotting the Games. Most of the Soviet‑allied nations of the Eastern Bloc joined the boycott in solidarity, despite the decision being hugely unpopular amongst Bloc countries with significant prior Olympic medal winnings.

On September 16, 1983, the California State Assembly and California State Senate approved Senate Joint Resolution 31, a measure urging President Ronald Reagan to ban the Soviets from participating in the Los Angeles Games. The non-binding resolution was hurriedly put forth by California State Senator John Doolittle in response to the Soviet shootdown of Korean Air Lines Flight 007 just 15 days prior. The resolution was reportedly amended to include the Olympic banning clause in the waning moments of the legislative session and that most of those voting for it did not know of the clause's inclusion. The only American Olympic official to speak out against the legislation was F. Don Miller, Executive Director of the U.S. Olympic Committee, who criticized what he termed "narrow‑minded legislators for trying to use the Olympics in American foreign policy". LAOOC President Peter Ueberroth and LAOOC Chairman Paul Ziffren both remained silent on passage of the legislation, saying they felt the best response was to "say nothing". In February 1984, the California State Senate advanced a bill to rescind the earlier legislation. The newer measure welcomed athletes from all nations to the Games and urged Californians to "be gracious hosts to all competitors".

Also in response to the shootdown of Korean Air Lines Flight 007 was the creation of a group calling itself the Ban the Soviets Coalition. Formed by evangelical Christian writer David Balsiger—a self-described "maverick Republican"—and three other Southern California businessmen approximately one month after the shootdown of Flight 007, the Coalition had as its stated goal the banning of Soviet athletes from competing at the L.A. Games. The Coalition initially sought out President Reagan to support their aims, but when that failed, the Coalition turned to more provocative actions, including sending letters to Soviet Olympic officials warning that their athletes might be physically harmed. Although relatively small in membership, the Coalition received outsized media attention at the time. The Soviets were to later make a great deal of the group in their warnings that Los Angeles was a dangerous place.

In April 1984, members of the Coalition met at a private home in the genteel residential enclave of Hancock Park, in Los Angeles, to discuss erecting billboards along freeways that the Soviet athletes would travel during the Games as a means of encouraging defection, saying they hoped to establish 500 safe houses for any defectors. The LAOOC was conspicuously absent in speaking out against these plans while the Reagan Administration similarly made no condemnation of the Coalition's activities. Worse still in Soviet eyes, was Deputy White House Chief of Staff Michael Deaver sending a friendly reply letter on January 10, 1984, thanking the Coalition for its earlier contact of the White House over concerns regarding proposed Soviet Olympic arrangements, such as docking the Soviet cruise ship MS Gruziya at Los Angeles-Long Beach Harbor, actions which the Coalition felt would "introduce adverse security implications" for the United States. Since Deaver was recognized as the Administration's chief liaison to the Olympic committee, the overtly friendly tone of his reply letter was immediately used in the Soviet press as proof that the Soviet team were unwelcome in Los Angeles.

LAOOC President Ueberroth belatedly tried reassuring the Soviets, first by telling them that the California legislative resolution was unimportant because of the "scatterbrained way it had been adopted", and second, by dismissing the Coalition as "fringe extremists, not a legitimate threat to athletes" who were ultimately "a group of nobodies in Los Angeles". A U.S. State Department memorandum had warned the Soviets that "the publicity that the Soviet media has devoted to the Ban the Soviets Coalition has generated far more interest and U.S. press coverage of this insignificant group than it could have ever achieved on its own." The Soviets in turn began requesting that demonstrations against Soviet athletes be banned, while also suggesting that Balsiger be forcibly removed from Los Angeles to "a remote and quiet place", leaving Deputy U.S. Secretary of State Kenneth Dam to ask "What more do they want, other than to change Los Angeles into a miniature of the Soviet Union?"

Near the end of April 1984, the Coalition began boasting to the media that they had infiltrated the LAOOC with operatives who were preparing to assist any Soviet athletes who came to the Games and wished to defect, prompting Ueberroth to label the group's leader Balsiger as "nutty". This led to the Coalition threatening to boycott all major Olympic Games' corporate sponsors if no public apology were forthcoming from Ueberroth. Ueberroth replied that he would "apologize if they'd change their name to a proper one ... maybe call themselves the Coalition to Hurt Athletes or maybe the Coalition to Play into the Hands of the Soviets." L.A. Police Chief Daryl Gates said of the Coalition, "I respect that group's First Amendment right to do what they are doing, but I can tell you that the Russian athletes would never be aware of theirs or any other peaceful demonstrations". Gates and Ueberroth never shared the Soviets' concern over the supposed strength of the Coalition's membership, with Gates stating he "couldn't believe that the Russians would be intimidated by a tiny group like the Ban the Soviets Coalition" and Ueberroth saying its members "could all get in a station wagon and drive south, and it would be the end of it".