Sir Anthony Eden, Earl of Avon, once the prime minister of Britain and three times its foreign secretary, died at his home yesterday in Wiltshire, England. He was 79.

He was visiting W. Averell Harriman, the American elder statesman, at the latter's winter residence near Palm Beach, Fla. last week when a liver ailment took a turn for the worse. When Eden's condition became serious, Prime Minister James Callaghan dispatched a Royal Air Force plane to bring him home.

Callaghan thus assured fulfillment of Eden's wish that he die in England.

The sending of the aircraft also was a tribute to a man who seemed to embody the best that was Britain in the Waning decades of her imperial glory. He fought in World War I, opposed Hitler and fascism when the policy of the British government was appeasement, served as the right hand of Sir Winston Churchill through tragedies and triumphs of World War II, and succeeded Churchill as prime minister in April 1955.

Only 21 months later, Eden's own career came to an abrupt close. He was forced from office by ill health and the outcry that followed the ill-starred. Anglo-French invasion of Suez that he directed in 1956. The purpose of the-expedition was to wrest control of the Suez Canal from Gamal Abdel Nasser, the late Egyptian president. But by then, the glory of the British Empire already had faded in fact if not in name.

In the minds of many, the Suez affair is a blight on Eden's reputation that provides the true measure of his abilities. For more than 25 years prior to that episode, however, he was at the very top of the second rank of worid leaders.

Formal messages of condolence from world leaders yesterday dwelt on Eden's successes and his strength of character - others might call it stubborness - rather than his failures.

Queen Elizabeth II said he had served his country "as a gallant soldier in the first world war and as a statesman in the second . . . He will be remembered in history above all as an outstanding diplomat and as a man of courage and integrity."

A statement issued by No. 10 Downing Street, the official residence of Prime Minister Callaghan, said: "To those who grew up in the '30s, Anthony Eden will always be remembered as a staunch opponent of fascism and the fascist dictators . . . We mourn the passing of a distinguished parliamentation and a statesman of exceptional experience and determination."

A White House spokesman said President Ford had sent telegrams expressing the "sympathy and sorrow" of the American people to Queen Elizabeth and to Lady Avon, who was at her husband's bedside when he died in his sleep.

"The President assured them that Lord Avon's long and distinguished career in government would form an important part of the history of this century," the spokesman said.

Secretary of State Henry A. Kissinger - with some of whose predecessors Eden ocassionally had disputes - said Eden was "one of the towering figures of this century's political scene . . . a stalwart leader of the British people in difficult and trying times."

In his lifetime, Eden enjoyed great popularity in his own country and a broad as much because of his good looks, his impeccable dress and his manner and because of his skill as a diplomat. (In matters of personal style such as appearance, he had no equal except, perhaps, the late Dean Acheson, former ULSL Secretary of State).

Eden fulfilled the popular idea of what an English gentleman should be. A significant part of this appeal came from his particularly distinguished combat record in World War I, in which Britain lost 1 million men.

The foreign press frequently - and erroneously - referred to hime as "Sir Anthony" or "Lord Eden." In fact, he was plain Mr. Anthony Eden until 1954, when he was dubbed a Knight of the Garter, the highest honor in the gift of the crown. He did not become a peer until 1961, when he was named Earl of Avon.

In the 1930s, when Churchill was a back-bench member of the House of Commons with a miniscule following. Eden was foreign secretary, the youngest man to hold that post in more than 80 years. He negotiated with Hitler, Mussclini and Stalin. He resigned in 1938 when he no longer could support Prime Minister Neville Chamberlain's efforts to bring "peace in our time" by accommodating Hitler.

He returned to office with the outbreak of World War II. Throughout the conflict and again in the 1950s until his final retirement, he took part in the great decisions and conferences that helped shape the post-war period. But always he operated in the shadow of Churchill, his friend and patron.

By his own account, it was the experience of these years that led Eden into the Seuz venture.

The insidious appeal of appeasement leads to a deadly reckoning," he wrote in his memoirs.

This was the situation in 1956. Israel had invaded the Sinai Peninsula. The United States withdrew an offer to help Egypt construct the Aswap High Dam on the Nile. Nasser nationalized the Suez Canal Co., which was largely owned by British and French interests, and announced he would use the canal revenues to finance the dam.

Eden regarded Nasser as an Arab Hitler. In his memoirs, he wrote:

"Nowadays it is considered immoral to recognize an enemy. Some say that Nasser is not Hitler or Mussolini. Allowing for a difference in scale, I am not so sure. He has followed Hitler's pattern, even to concentration camps and the propogation of "Mein Kampf" among his officers. He has understood and used the Goebbels pattern of propaganda in all its lying ruthlessness. Egypt's strategic position increases the threat to others from any aggressive militant dictatorship there."

He addressed the possibility of doing nothing in the face of Nasser's action and rejected it.

"I thought and think that failure to act would have brought the worst of consequences, just as I think the world would have suffered less if Hitler had been resisted on the Rhine, in Austria or in Czechoslovakia, rather than in Poland. This will be for history to determine."

However history determines that question, the lessons that Anthony Eden had learned earlier in the highest reaches of international politics led him - when he finally got his hands on the reins of power - to actions that ended on otherside brilliant career.

After his retirement in 1957, Eden spent much of his time at his country home, The Manor House, Alvediston, on the Salisbury Plain. As Earl of Avon, he spoke occassionally in the House of Lords on foreign affairs, but his public appearaces were few, partly because of the poor health that he had suffered intermittently from the early 1950s.

He finished his three-volume memoirs in 1965. The following year, he published an article criticizing the United States for its deepening involvement in Vietnam. He said the United States must negotiate a settlement of the conflict.

In a television interview at the same time, he said that the U.S. bombing of North Vietnam could never settle the problems in South Vietnam.

"On the contrary, bombing creates a sort of 'David and Goliath' complex in any country that has to suffer - as we had to, and as I expect the Germans had to, in the last war," he said.

It was over the fate of Vietnam that Eden had his first serious disagreement with John Foster Dulles. President Eisenhower's first secretary of state.It came at the 1954 Geneva Conference at which it was agreed that the French would withdraw from Indochina and that free elections would be held in North and South Vietnam. Dulles opposed the elections on the grounds that Ho Chi Minh would not permit them to be free in North Vietnam.

Dulles also refused to support the Suez operation, wishing to work through the United Nations instead, and this further worsened relations with Eden.

In 1969, former Prime Minister Sir Harold MacMillau, Eden's successor, told an interviewer on the BBC that it was not only because of Vietnam and Suez that Eden disliked Dulles, and in so doing MacMillan gave a brief glimpse of Eden the man in contrast to Eden the statesman.

"Eden was sensitive, charming, gay, debonair, frightfully well-informed without ever showing it," MacMillan said. "And so when Dulles would tell you - would take about three-quarters of an hour to tell you - something you knew, practically learned when you were at school, you had to have a good deal of self-control."

Robert Anthony Eden was born on June 12, 1897, at Windlestone Hall in the County of Durham, where the Edens had been prominent members of the landed gentry for several centuries. His father, Sir William Eden, was a baroret and an eccentric devoted to fox-hunting, shooting, and art, and given to wild outbursts of temper.

His mother, Sybil, Lady Eden, was a member of the Grey family, one of whose members was prime minister during the passage of the Reform Bill of 1832, a measure which opened the doors or political power to the middle class.

Another of Eden's ancestors was Sir Robert Eden, the last of the royal governors of Maryland.

Young Eden was educated first by tutors and then sent to boarding school at the age of 9 to prepare for Eton, one of Britain's great training grounds for its elite. He was a student there when World War I broke out in 1914. In 1915, at 18, he entered the army and joined the King's Royal Rifle Corps.

The war, he wrote in his memoirs, "saw the destruction of the world as I knew it."

Two of his brothers were killed. His father died. A third brother was interned in Germany. An uncle was shot down and captured. A brother-in-law was seriously wounded. It is said that one-third of his bousemates at Eton were killed.

Eden escaped without injury, although he took part in some of the heaviest fighting from 1916 until the end of the war in 1918. He won the Military Cross for saving the life of his platoon sergeant who was wounded and pinned down by machine gun fire, became the adjutant of his batalion at the age of 19, and the youngest brigade major in the British army at the age of 20. He finished the war a captain.

When he visited Hitler as British foreign secretary in 1935. Eden and his host discovered that they had fought along the same part of the line during the great German offensive of 1918. The German press referred to him with approval as a "front-soldat."

"We were virtually opposite each other and on the back of our memucard we drew our line, and where everybody was, much more than I think an average corporal could be expected to know."

After the dinner, the then French Ambassador to Germany, Andre Francois-Poncet, said to Eden: "And you missed him. You ought to be show."

After the war, Eden went to Christ Church College, Oxford, where he won first class honors in Persian and Arabic. He took his degree in 1922 and briefly considered a career in the foreign service, but decided on politics instead.

The same year he finished Oxford he lost an election to Parliament from his home constituency, the Spennymore Division of Durham. A year later, he was elected to the House of Conamons for Warwick and Leamington. He held that seat until he resigned it in 1957.

Just before entering Parliament, he married Beatric Beckett, the daughter of Sir Gervase Beckett, one of the owners of the Yorkshire Post. The newspaper was one of the few in Britain that joined Eden in opposing appeasement of Hitler in the 1930s.

Eden began his rise to prominence as the parliamentary private secretary to Sir Austin Chamberlain, the foreign secretary, from 1926 to 1929. In 1931, he became a member of the government as parliamentary under secretary for foreign affairs. He first entered the Cabinet as Lord Privy Seal in 1934. For a brief period in 1935 he was minister for League of Nations Affairs and then, in the same year, became foreign secretary, a post he held until his break with the government over dealing with Hitler in 1938.

On the outbreak of World War II in September 1939, he was called back to office as secretary of state for dominion affairs. He then became secretary of war. Late in 1940, Churchill, who became prime minister in May, 1940, named him foreign secretary for the second time. He held that post until the Conservative Party, of which he was a member throughout his career, was defeated by the Labor Party in 1945.

He became foreign secretary for the third time following the Conservatives' return to power in 1961. He held the office until he succeeded Churchill as prime minister in 1955.

Eden did not find his rule as Churchill's heir apparent easy. Churchill gave him this rule early in World War II and put it in writhing in a letter to King George VI in June, 1942. "The long era as crown prince was established," Eden wrote of Churchill's action, "a position not necessarily enviable in politics."

But the two men remained close. In 1950, Eden divorced his first wife on the ground of desertion, a step which diminished his chances of becoming prime minister in the Britain of that time.

In 1952, he married Clarissa Anne Spencer Churchill, Churchill's niece.

The Church of England disapproved the marriage of divorced persons, and despite a plea from Churchill to the archishop of Canterbury, the couple had to be married in a civil ceremony.

It was in these years that Eden's health began to fail him. In 1953, he underwent a series of operations in Boston for the removal of gallstones. He returned to Boston in 1957 for replacement of a bile duct. In 1962, he underwent surgery for removal of a non-cancerros growth in his chest.

These difficulties did not prevent him from pursuing many of his lifelong interests. As a younger man, he was an avid tennis player. He was a trustee of the National Gallery of Art for several years and continued his interest in art.