AIG history dates back to 1919, when Cornelius Vander Starr established an insurance agency in Shanghai, China. Starr was the first Westerner in Shanghai to sell insurance to the Chinese, which he continued to do until AIG left China in early 1949—as Mao Zedong led the advance of the Communist People's Liberation Army on Shanghai.Starr then moved the company headquarters to its current home in New York City. The company went on to expand, often through subsidiaries, into other markets, including other parts of Asia, Latin America, Europe, and the Middle East.

In 1962, Starr gave management of the company's lagging U.S. holdings to Maurice R. "Hank" Greenberg, who shifted its focus from personal insurance to high-margin corporate coverage. Greenberg focused on selling insurance through independent brokers rather than agents to eliminate agent salaries. Using brokers, AIG could price insurance according to its potential return even if it suffered decreased sales of certain products for great lengths of time with very little extra expense. In 1968, Starr named Greenberg his successor. The company went public in 1969.

Beginning in 2005, AIG became embroiled in a series of fraud investigations conducted by the Securities and Exchange Commission, U.S. Justice Department, and New York State Attorney General's Office. Greenberg was ousted amid an accounting scandal in February 2005; he is still fighting civil charges being pursued by New York state.The New York Attorney General's investigation led to a $1.6 billion fine for AIG and criminal charges for some of its executives.Greenberg was succeeded as CEO by Martin J. Sullivan, who had begun his career at AIG as a clerk in its London office in 1970.

On June 15, 2008, after disclosure of financial losses and subsequent to a falling stock price, Sullivan resigned and was replaced by Robert B. Willumstad, Chairman of the AIG Board of Directors since 2006. Willumstad was forced by the US government to step down and was replaced by Edward M. Liddy on September 17, 2008.