Henri Bonnet, 90, the French ambassador to the United States from 1944 to 1955, died Wednesday night in a Paris hospital, his family announced yesterday.

Mr. Bonnet took up his post here at a time of deep trauma in his nation's history. France had been defeated by the Germans during World War II. Part of the country had been ruled for part of the war by a puppet government in Vichy. The Vichy government was discredited in Washington as well as in many other capitals.

Only the Free French movement, led by Gen. Charles de Gaulle, respresented the true France, in the minds of many Americans and others. It was under de Gaulle's leadership that Mr. Bonnet came to Washington as his country's diplomatic representative.

During the years that he held the post, Mr. Bonnet succeeded in restoring and maintaining his country's prestige in the eyes of Washington. Throughout he was assisted by his wife, the Greek-born Helle Bonnet, a woman of style and beauty and one of the capital's most successful hostesses.

It was a time of upheaval on the world scene. The Cold War began in Europe. The Marshall Plan was initiated to put the economy of Western Europe on its feet and enable it to withstand the pressures of Soviet communism. Elsewhere, the colonial empires were beginning to break up. France became involved in a disastrous war in INdochina. Trouble loomed in Algeria and elsewhere in North Africa. Governments in Paris succeeded each other with sometimes bewildering rapidity.

So effective was Mr. Bonnet that The Washington Post noted in an editorial when his retirement was announced that "the Bonnets, aided by a liberal dispensation of Legion of Honor ribbons, were able to offset all the vicissitudes in Paris.

"In their vicinity the truth about conditions inside France, in North Africa, and about Indochina was either dissolved in doubt or blurred in hope. That both the Democratic and Republican administrations have been thoroughly misled time after time about events in France and France overseas is a mark of our credulity. But from the standpoint of the French, it was an achievement, and the diplomacy of the Bonnets should be given some of the credit."

Although he was not a diplomat by profession, Mr. Bonnet spent most of his life on the international scene. He was born at Chateauponsac, France, studied at the Ecole Normale Superieure, and became an instructor at the University of Paris. During World War I he served in the French army, rose to the rank of captain and was decorated with the Croix de Guerre and made an officer of the Legion of Honor.

Mr. Bonnet spent the years from 1920 to 1931 as a member of the secretariat of the League of Nations in Geneva. He returned to Paris to head the International Institute of Intellectual Cooperation, an organization devoted to seeking cooperation on scientific and political problems. He escaped to England when the Germans invade France in 1940.

In New York, he became vice president of France Forever, the Free French group in the United States. In 1943, Gen. de Gaulle summoned him to Algiers, where he became a member of the committee of national liberation, the Free French government. When that government was recognized by the United States, he was sent to Washington as ambassador.

After his retirement from here, Mr. Bonnet was president of the Franco-American Committee for Industrial Cooperation. He was active in several other international groups as well.

His wife, whom he married in 1932, died in 1962.