King Juan Carlos I of Spain will deliver this year's Commencement address, University officials announced yesterday.

Juan Carlos, whom many have credited with guiding his country from authoritarianism to democracy, is the only first-choice candidate to accept Harvard's offer in four years.

The monarch's speech will address Spanish-American relations, David A. Aloian '49, executive director of the Harvard Alumni Association which runs the Commencement exercises, said yesterday.

This year's announcement comes on the earliest date ever, Aloian added. In fact, Juan Carlos accepted in December, but the Alumni Association decided to keep the information under wraps until later in the year.

A statement was released yesterday because "We decided that there was no way we could keep this a secret late into the spring," Aloian added.

Last year, the Mexican author Carlos Puentes was named Commencement speaker on May 19, a mere three weeks before the ceremonies, after a much-publicized offer to Polish union leader Lech Walesa fell through (See story below.)

This year, in contrast, the offer was out by October, tentatively accepted by November, and officially accepted in December, Aloian said.

Juan Carlos the Man

The King of Spain is described as both a forceful, charismatic leader and a humble father of three.

The hand-picked successor to Generalissimo Francisco Franco--who ruled Spain with an iron grip from 1939 to his death in 1975--Juan Carlos succeeded to the throne and promptly instituted a constitutional monarchy.

"It was so quick that you didn't know the policies of who you were voting for." Juan Corbello '85, a transfer student from the University of San Louis in Madrid, said yesterday.

The transition earned Juan Carlos an international reputation, Corbello added, as well as a nomination for a Nobel Peace Prize.

"He has become a symbol of democracy and political negotiations," said Terry L. Karl, assistant professor of Government.

"This transition is really one of the great success stories of foreign affairs," added Robert D. Putnam, professor of Government.

But by all accounts, Juan Carlos has not let success go to his head. Since he warded off a military coup in 1981, the urbane, cosmopoli- lan monarch has lived modestly in his palace in Madrid.

"The king sometimes has called this son's high school and asked for the son be absent, like an ordinary father," said Juan Marichal Smith Professor of the French and Sparnth Languages and Literatures.

When skiing Juan Carios "waits in the lift line with everyone else." Marichal added.

And according to Corbello, "He lives in a smaller house than the First Minister... and has less security too."

But the down home king has maintained his political profile. Through a state trip to South Aamerica last year, Juan Carlos has offered his advice as a veteran of democratization.

"He represents more than the past the future for Latin America the possibility of a democratic future for Spanish-speaking nations," said Marichal.

Public response in South America to the visit was overwhelmingly positive Uruguayan people shouted "Long live the democratic king!" to the dismay of the country's military government and Venezuela gave him the Bolivar Medal in honor of "the Liberator," Simon Bolivar.

Juan Carles, who comes from the centuries-old Bourbon dynasty, was born in 1936 in Rome, where his family moved during the Spanish Civil War. He returned to Spain at age nine and was educated in the military and the law. His wife, Princess Sophia of Greece, has a Ph.D. and reportedly teaches at the University of Madrid. The couple has three children--two daughters and a son--in high school in Madrid.

Each of the last three years, internationally prominent figures have turned down Harvard's offer to speak at Commencement. Three years ago. President Reagan declined Harvard's offer, and Thomas J. Watson Jr., former U.S. ambassador to the Soviet Union and chairman of IBM, gave the address.

Two years ago Harvard selected Professor of Greek Emeritus John H. Finley '25, after Jihan Sadat, widow of the slain Egyptian leader, said she could not make it.

Last year, Fuentes accepted when Walesa sent word that he feared permanent exile if he came to Harvard to speak