The archdiocese said he died peacefully shortly after 3 a.m. He had been in declining health for years.
Hannan was the 11th archbishop in New Orleans history and one of the most active. When he turned 75 and had to retire as archbishop, he became president of WLAE-TV, the public television station he founded.
Assigned to New Orleans in 1965 from Washington, where he had been auxiliary bishop since 1956, he found the old St. Louis Cathedral, in the middle of an area of the French Quarter a-swarm with tourists, street performers, tarot card readers and musicians, had a unique pleasure for a churchman.
"This is the only city where an archbishop can walk into his cathedral while a band outside in Jackson Square is playing `When the Saints Go Marching In,"' he said.
When Kennedy was assassinated Nov. 22, 1961, his widow, Jacqueline, asked Hannan to deliver the eulogy because of his close personal relationship with the president, which dated back to the 1940s. Then-Father Hannan became friends with Kennedy by smoothing over a misunderstanding that Kennedy had with a Jesuit priest.
He also officiated at a quiet reburial of two Kennedy infants in 1964 so their bodies could be near their father's in Arlington National Cemetery.
"We did it in the middle of the night, and so quietly that we caught everyone off guard," Hannan said in 1965. "Not even the Army chauffeurs knew where they were going when they picked us up."
In 1968, Hannan returned to Washington from New Orleans to give the graveside eulogy for Sen. Robert. F. Kennedy.
When Jacqueline Kennedy Onassis died of cancer in 1994, Hannan was again at Arlington to preside at a brief service preceding her burial.
As New Orleans' archbishop, Hannan combined conservative politics and service to the poor.
Highlights of his tenure as archbishop included the 1987 visit of Pope John Paul II - a visit that Hannan began angling for in 1984. After a while, said Hannan, "Every time he saw me, he'd simply say, `New Orleans! New Orleans!"'
Hannan lost a struggle to block the "no nukes" pastoral letter approved by the nation's Catholic bishops in Chicago in 1983. He argued that the politics inherent in the letter could not help disarmament talks.
"Obviously, if the Russians think that 50 million Catholics are going to believe that we must say a `no' to nuclear war ... then, of course, we have no strength from which to argue for disarmament," he said.
Despite what were labeled conservative views, Hannan had few peers in liberal social action.
He said he decided to push the diocese to serve the poor when he walked through the city's squalid public housing projects in 1965, shortly after his transfer from Washington.
Hannan created what was at the time the largest housing program for the elderly - 2,780 units - of any U.S. diocese. The archdiocese also operates one of the biggest Catholic Charities in the nation. When Hannan stepped down, its $20 million budget was helping more than 47,000 people a year.
Under his guidance, the church set up a hospice for AIDS patients. He said there was no contradiction in a ministry for homosexuals and drug addicts.
"We disapprove, too, of people being alcoholics or drinking too much. But we sure try to take care of them if they have that problem," he said.
Hannan was born in Washington, D.C., the fourth of eight children born to an Irish immigrant and a fourth-generation Washingtonian. His late sister, Dr. Mary Mahoney, once was president of the National Conference of Catholic Women.
He was ordained in Rome in 1938 and served two years at a church in Baltimore, then volunteered as a paratroops chaplain in World War II, getting the nickname "The Jumping Padre."
When U.S. troops took the city of Cologne, Germany, Hannan dodged through front lines to the cathedral, had himself appointed temporary pastor, and, when the fighting passed, posted Army guards to prevent looting or more damage.
In 1945, Hannan helped liberate a camp of starving prisoners from the German prisoner of war camp at Wobbelin. He was discharged in 1946 with the rank of major.
After the war, he served in the Washington archdiocese, moving up to auxiliary bishop in 1956.
Decades after he left Washington, Hannan still chuckled about the time President Truman, a card-playing Baptist, called him for a discreet visit to the Oval Office.
"Harry Truman had just been bawled out by his pastor ... for proposing an ambassador to the Holy See. Now he was calling in a priest to bless a huge St. Christopher medal for a new presidential airplane."