Galbraith was 97. He died of natural causes on Saturday night at Mount Auburn Hospital in Cambridge, where he was admitted nearly two weeks ago, Alan Galbraith said.
During a long career, the Canadian-born economist served as adviser to Democratic presidents from Franklin D Roosevelt to Bill Clinton, and was John F Kennedy's ambassador to India.
"He had a wonderful and full life," his son said.
Galbraith, who was outspoken in his support of government action to solve social problems, became a large figure on the American scene in the decades after World War II.
He was one of America's best-known liberals, and he never shied away from the label.
"There is no hope for liberals if they seek only to imitate conservatives, and no function either," Galbraith wrote in a 1992 article in Modern Maturity, a publication of the American Association of Retired Persons.
The Affluent Society
One of his most influential books, The Affluent Society, was published in 1958.
It argued that the American economy was producing individual wealth but has not adequately addressed public needs such as schools and highways.
US economists and politicians were still using the assumptions of the world of the past, where scarcity and poverty were near-universal, he said.
"The total alteration in underlying circumstances has not been squarely faced," he wrote.
Galbraith was John F Kennedy's
ambassador to India
"As a result, we are guided, in part, by ideas that are relevant to another world. ... We do many things that are unnecessary, some that are unwise, and a few that are insane."
In 1999, a panel of judges organised by the Modern Library, a book publisher, picked The Affluent Society as number 46 on its list of the century's 100 best English-language works of nonfiction.
Galbraith also was known for his theories on countervailing forces in the economy, where groups such as labour unions were needed to strike a political and social balance.
Richard Neustadt, a Harvard colleague who also served as an aide to presidents Kennedy and Truman, said Galbraith demonstrated how "you have to empower people directly before they could fight for themselves".
Galbraith, greeted by the Great Depression when he graduated from college, also had "much more confidence in the ability to work out of economic difficulties and do so with the help of government", Neustadt said.
After his retirement from Harvard in 1975, Galbraith gained fresh recognition as host of the British-made television series, The Age of Uncertainty.
His book under the same title was a best seller, as was Almost Everyone's Guide to Economics.
Among his other books were The Great Crash, 1955, and The Culture of Contentment, 1992.
"It is not usual for a man past his 90th birthday to write a book that is as fresh and lively as the work of a 30-year-old. But John Kenneth Galbraith is not a usual man, and he has done it"
The New York Times
He returned to the theme of the crash of 1929 in a January 1987 Atlantic Monthly article that correctly predicted that year's market plunge by citing the parallels of the two eras.
In 1988, he and Soviet economist Stanislav Menshikov wrote Capitalism, Communism and Coexistence: From the Bitter Past to a Better Prospect.
The book is a compilation of discussions conducted at Galbraith's summer home in Townsend, Vermont, about socialism and capitalism.
Galbraith's 1996 book, The Good Society, outlined his blueprint for enriching America economically and socially, while his 1999 book, Name-Dropping: From FDR On, was a lighthearted look at his encounters with everyone from Eleanor Roosevelt onward.
"It is not usual for a man past his 90th birthday to write a book that is as fresh and lively as the work of a 30-year-old. But John Kenneth Galbraith is not a usual man, and he has done it," The New York Times wrote about Name-Dropping.
Galbraith was born October 15, 1908, in Iona Station, Ontario, Canada.
After graduating from the University of Toronto in 1931, Galbraith moved to the US where he earned his PhD in economics from the University of California.
He taught at Harvard from 1934 to 1939 and at Princeton University from 1939 to 1942, then worked in the federal Office of Price Administration during the war years.
Galbraith returned to Harvard in 1948, remaining active on the faculty until his retirement.
He was the recipient of the Medal of Freedom, awarded by Truman in 1946, and another one from Clinton in 2000. The professor also served as president for a term of the American Economic Association.