On May 25, 1948, a former United States Army flier entered the American Embassy in Paris, renounced his American citizenship and, as astonished officials looked on, declared himself a citizen of the world.

In the decades that followed, until the end of his long life last week, he remained by choice a stateless man — entering, leaving, being regularly expelled from and frequently arrested in a spate of countries, carrying a passport of his own devising, as the international news media chronicled his every move.

His rationale was simple, his aim immense: if there were no nation-states, he believed, there would be no wars.

Garry Davis, a longtime peace advocate, former Broadway song-and-dance man and self-declared World Citizen No. 1, who is widely regarded as the dean of the One World movement, a quest to erase national boundaries that today has nearly a million adherents worldwide, died on Wednesday in Williston, Vt. He was 91, and though in recent years he had largely ceased his wanderings and settled in South Burlington, Vt., he continued to occupy the singular limbo between citizen and alien that he had cheerfully inhabited for 65 years.

“I am not a man without a country,” Mr. Davis told Newsweek in 1978, “merely a man without nationality.”

Mr. Davis was not the first person to declare himself a world citizen, but he was inarguably the most visible, most vocal and most indefatigable.

The One World model has had its share of prominent adherents, among them Albert Schweitzer, Jean-Paul Sartre, Albert Einstein and E. B. White.

But where most advocates have been content to write and lecture, Mr. Davis was no armchair theorist: 60 years ago, he established the World Government of World Citizens, a self-proclaimed international governmental body that has issued documents — passports, identity cards, birth and marriage certificates — and occasional postage stamps and currency.

He periodically ran for president of the world, always unopposed.

To date, more than 2.5 million World Government documents have been issued, according to the World Service Authority, the group’s administrative arm.

Whether Mr. Davis was a visionary utopian or a quixotic naïf was long debated by press and public. His supporters argued that the documents he issued had genuine value for refugees and other stateless people.

His detractors countered that by issuing them — and charging a fee — Mr. Davis was selling false hope to people who spent what little they had on papers that are legally recognized almost nowhere in the world.

What is beyond dispute is that Mr. Davis’s long insistence on the inalienable right of anyone to travel anywhere prefigures the present-day immigration debate by decades. It likewise anticipates the current stateless conditions of Julian Assange and Edward J. Snowden.

Mr. Davis, who spoke about the One World movement on college campuses and wrote books on the subject, seemed impervious to his critics. In a voice trained to be heard in the last balcony (he was once a Broadway understudy to Danny Kaye), he would segue with obvious relish into a series of minutely reasoned arguments concerning the need for a world without nationalism.

“The nation-state is a political fiction which perpetuates anarchy and is the breeding ground of war,” he told The Daily Yomiuri, an English-language newspaper in Japan, in 1990. “Allegiance to a nation is a collective suicide pact.”

The quest for a unified earth was an objective on which Mr. Davis had trained his sights very early. It was born of his discomfort with a childhood of great privilege, his grief at the loss of a brother in World War II and his horror at his own wartime experience as a bomber pilot.

Sol Gareth Davis was born in Bar Harbor, Me., on July 27, 1921, a son of Meyer Davis and the former Hilda Emery.

Meyer Davis was a renowned society orchestra leader known as the “millionaire maestro”: at his height, he presided over an empire of 80 ensembles — employing more than a thousand musicians — which played at debutante balls, national political conventions and White House inaugurations.

Garry was reared in Philadelphia in a glittering milieu in which the family car was a chauffeured Rolls-Royce and family friends included Bob Hope and Ethel Merman. As a young man he was considered unserious, he later said, known for roguish wit but lacking direction.

After studying theater at the Carnegie Institute of Technology in Pittsburgh, Mr. Davis made his Broadway debut in October 1941 in a small role in “Let’s Face It!,” the musical comedy. He was also the understudy for its star, Mr. Kaye.

Then the United States entered the war. Mr. Davis and his older brother, Meyer Jr., known as Bud, went overseas — Bud with the Navy and Garry with the Army Air Forces, flying B-17 bombers. Bud Davis did not return: he was killed in 1943, when his ship, the destroyer Buck, was sunk off the coast of Italy by a German submarine.

That, and a dark epiphany during a bombing run over Brandenburg, Germany, Garry Davis later wrote, would alter his life’s course.

“Ever since my first mission over Brandenburg, I had felt pangs of conscience,” Mr. Davis wrote in a 1961 memoir, “The World Is My Country.” (The volume was later reissued as “My Country Is the World.”) “How many bombs had I dropped? How many men, women and children had I murdered? Wasn’t there another way, I kept asking myself.”

The other way, he came to believe, was to eradicate conflict by eradicating borders.

In November 1948, six months after renouncing his citizenship in Paris, Mr. Davis stormed a session of the United Nations General Assembly there.

“We, the people, want the peace which only a world government can give,” he proclaimed. “The sovereign states you represent divide us and lead us to the abyss of total war.”

His act, reported worldwide, earned the support of the intelligentsia, including Albert Camus, and of the French public, so recently racked by war. Less than two weeks later, speaking at a Paris auditorium, Mr. Davis drew a crowd of 20,000.

In 1949, Mr. Davis founded the International Registry of World Citizens and was soon inundated with requests to join from around the globe. “We’re bigger than Andorra,” he told The Boston Globe in 1981, when the registry was a quarter-million strong.

Today, more than 950,000 people are registered world citizens, according to the World Service Authority, based in Washington.

Mr. Davis, who lived for long periods in France, appeared on Broadway a few more times in the early 1950s, including in a revue called “Bless You All” and “Stalag 17,” the prisoner-of-war drama. But the One World imperative occupied him increasingly.

In 1953, he founded the World Government of World Citizens. The demand for its documents proved so brisk that he established the service authority the next year.

More than half a million world passports have been issued, though there are no statistics on the number of people who have successfully crossed borders with them. A half-dozen countries — Burkina Faso, Ecuador, Mauritania, Tanzania, Togo, Zambia — have formally recognized the passport. More than 150 others have honored it on occasion, according to the service authority.

Fees for the passport range from $45 (valid for three years) to $400 (for 15 years). The passport has text in seven languages, including Esperanto, the artificial international language.

Carrying world passport No. 1, Mr. Davis spent decades spreading his message, slipping across borders, stowing away on ships, sweet-talking officials, or wearing them down, until they let him in. The newspapers charted his comings and goings:

1949: “Garry Davis Arrested in Paris”; 1953: “Garry Davis Held Again: Arrested When He Camps Out Near Buckingham Palace”; 1957: “France Expels Garry Davis”; 1979: U.S. Court Rules ‘World Citizen’ Davis Is an Alien and Rejects His Passport; 1984: “Japan Expels American ‘World Citizen’ ”; 1987: “ ‘World Citizen’ Announces Presidential Bid.” (It was the United States presidency this time.)

In 1986, Mr. Davis ran for mayor of Washington, receiving 585 votes.

Mr. Davis was arrested dozens of times, usually for attempting to enter a country without official papers. He had canny ways of circumventing authority.

In the 1950s, when France was trying to deport him, he conspicuously shoplifted items from a Paris department store. (His haul, United Press reported, was “$47 worth of peach-colored lace panties, black-silk brassieres, black garter belts, lace petticoats and pink slips.”) He made certain he was arrested.

As a result of his arrest, Mr. Davis was legally enjoined from leaving the country.

Mr. Davis was married two or three times, depending on how one counts. His first marriage, to Audrey Peters, an American whom he courted by mail while detained in France and whom he met for the first time two weeks before their wedding in 1950, ended in divorce. In 1954, the newspapers reported his “marriage” at sea to Gloria Sandler in a ceremony he performed himself; that union, too, was dissolved. His marriage to Esther Peter in 1963 also ended in divorce.

Survivors include a daughter, Kristina Starr Davis, from his marriage to Ms. Peters; two sons, Troy and Kim, and a daughter, Athena Davis, who confirmed her father’s death, from his marriage to Ms. Peter; a sister, Ginia Davis Wexler; a brother, Emery; and a granddaughter.

His other books include “World Government, Ready or Not!” (1984) and “Dear World: A Global Odyssey” (2000). He was the subject of a short documentary, “One! The Garry Davis Story,” released in 2007.

In old age, Mr. Davis was far from idle. Last year, he had a world passport delivered to Mr. Assange, the founder of WikiLeaks, who has been holed up in the Ecuadorean embassy in London.

Just weeks before he died, Mr. Davis had a world passport sent, via Russian authorities, to Mr. Snowden, the fugitive former national security contractor accused of violating espionage laws, whose United States passport was revoked in June.

Mr. Snowden could not be reached for comment.