The American Israel Public Affairs Committee (AIPAC /ˈeɪpæk/ AY-pak) is a pro-Israel lobbying group that advocates its policies to the legislative and executive branches of the United States. It is one of several pro-Israel lobbying organizations in the United States, and has been called one of the most influential lobbying groups in the U.S.

AIPAC was founded in 1954 by Isaiah L. Kenen, a lobbyist for the Israeli government, partly to counter negative international reactions to Israel's Qibya massacre of Palestinian villagers that year. AIPAC became a powerful organization during the 1980s. In 2002, it expressed intent to lobby Congress to authorize use of force in Iraq, and in 2003, the Iraq War was defended at AIPAC events. In 2005, a Pentagon analyst pleaded guilty to espionage charges of passing U.S. government secrets to senior AIPAC officials, in what became known as the AIPAC espionage scandal.

Until 2021, AIPAC did not raise funds for political candidates itself; its members raised money for candidates through political action committees unaffiliated with AIPAC and by other means. In late 2021, AIPAC formed its own political action committee and announced plans for a Super PAC, which can spend money on candidates' behalf. AIPAC's critics have said it acts as an agent of the Israeli government and that it has a "stranglehold" on the United States Congress. AIPAC has been accused of being strongly allied with Israel's Likud party and the U.S. Republican Party. An AIPAC spokesman has called this a "malicious mischaracterization".

AIPAC describes itself as a bipartisan organization. It says it has five million members, 17 regional offices, and "a vast pool of donors". AIPAC's supporters say its bipartisan nature can be seen at its yearly policy conference, which in 2016 included both major parties' nominees: Democrat Hillary Clinton and Republican Donald Trump. AIPAC has been criticized as unrepresentative of American Jews who support Israel and supportive only of right-wing Israeli policy and viewpoints.

Journalist and lawyer Isaiah L. Kenen founded the American Zionist Committee for Public Affairs (AZCPA) as a lobbying division of the American Zionist Council (AZC), and they split in 1954. Kenen, a lobbyist for the Israeli government, had at earlier times worked for the Israeli Ministry of Foreign Affairs. As a lobbyist, Kenen diverged from AZC's usual public relations efforts by trying to broaden support for Israel among traditionally non-Zionist groups. The founding of the new organization was in part a response to the negative international reaction to the October 1953 Qibya massacre, in which Israeli troops under Ariel Sharon killed at least sixty-nine Palestinian villagers, two-thirds of them women and children. As the Eisenhower administration suspected the AZC of being funded by the government of Israel, it was decided that the lobbying efforts should be separated into a separate organization with separate finances.

In 1959, AZCPA was renamed the American-Israel Public Affairs Committee, reflecting a broader membership and mission. Kenen led the organization until his retirement in 1974, when he was succeeded by Morris J. Amitay. According to commentator M.J. Rosenberg, Kenen was "an old-fashioned liberal," who did not seek to win support by donating to campaigns or otherwise influencing elections, but was willing to "play with the hand that is dealt to us."

By the 1970s, the Conference of Presidents of Major American Jewish Organizations and AIPAC had assumed overall responsibility for Israel-related lobbying within the Jewish communal landscape. The Conference of Presidents was responsible for speaking to the Executive Branch of the U.S. government, while AIPAC dealt mainly with the Legislative Branch. Although it had worked effectively behind the scenes since its founding in 1953, AIPAC only became a powerful organization in the 15 years after the Yom Kippur War in 1973.

By the mid-1970s, AIPAC had achieved the financial and political clout necessary to sway congressional opinion, according to former Israeli Diplomat to the United States Michael Oren. During this period, AIPAC's budget soared from $300,000 in 1973 to over $7 million during its peak years of influence in the late 1980s. Whereas Kenen had come out of the Zionist movement, with early staff pulled from the longtime activists among the Jewish community, AIPAC had evolved into a prototypical Washington-based lobbying and consulting firm. Leaders and staffers were recruited from legislative staff and lobbyists with direct experience with the federal bureaucracy. Confronted with opposition from both houses of Congress, United States President Gerald Ford rescinded his 'reassessment.'" George Lenczowski notes a similar, mid-1970s timeframe for the rise of AIPAC power: "It [the Jimmy Carter presidency] also coincides with the militant emergence of the American Israel Public Affairs Committee (AIPAC) as a major force in shaping American policy toward the Middle East."