His son James Harrison told The New York Times his father died Thursday at a hospice.
The elder Harrison bought the publication in 1953 and ran it until 1974 and it rarely made money. He told the Times the year he sold it for $380,000.
He told the newspaper losses at the magazine were as high as $200,000 a year.
Under his tenure, the liberal weekly magazine was a strong voice on behalf of the civil rights movement and after initially supporting the Vietnam War became a relentless critic of it.
"He was an old-fashioned gentleman who treated everybody as if they were part of the literary set," said Walter Pincus, a Washington Post reporter who once worked for Harrison. "You really had to read it when Gil had it, if you were part of the liberal left."
Harrison is survived by three sons, a daughter and five grandchildren.