Adolfo Suarez, Spain's first democratically elected prime minister after decades of right-wing rule under General Francisco Franco, has died aged 81.
Suarez died on Sunday afternoon (local time) in Madrid's Cemtro Clinic hospital, family spokesman Fermin Urbiola said. Suarez had been suffering from Alzheimer's disease for a decade.
The cause of death was "chronic obstructive pulmonary disease made worse within the context of Alzheimer's disease", said Dr Isabel de la Azuela of Cemtro.
Suarez had been admitted to the hospital Monday with pneumonia. On Friday, his son Adolfo said his condition had deteriorated and that he was expected to die within days.
King Juan Carlos, in a televised address, expressed his gratitude to Suarez for his "loyalty to the crown" and sadness over his death.
"Suarez was a statesman who put the whole of the Spanish nation ahead of his personal and party interests," the king said.
Prime Minister Mariano Rajoy said "one of the great men of our era has left us", and declared three days of national mourning.
Suarez became secretary-general of the National Movement, which was Spain's only party during Franco's rule, and also was director-general of state television broadcaster TVE.
He was 43 when he was chosen in 1976 by King Juan Carlos to lead the country toward a democratic parliamentary monarchy after Franco's death a year earlier. Suarez had the king's trust and the two were close.
"King Juan Carlos chose Suarez because he knew him, had followed his career since he was Civil Governor, knew how he thought, knew his daring, his loyalty and because Suarez had hit the nail on the head by including the words democracy and monarchy in the same broadcast package," said Fernando Onega, a government spokesman in Suarez's Cabinet.
Despite opposition to his appointment from many centrist and leftist politicians, Suarez and the Democratic Center Union party he had founded won the first post-Franco elections the following year.
Under Suarez's leadership the new Parliament approved a democratic constitution in 1978, a milestone that proved popular enough to enable him and his party to win re-election the following year.
During his time in office, Suarez surprised his critics and antagonised the army and church by legalising political parties and trade unions and calling for an amnesty for political offences, steps that were seen as decisive after Franco's 1939-1975 authoritarian rule.
Suarez was considered a skilled and determined crisis manager during the transition to democracy, but proved to be less successful as a day-to-day organiser. Eventually - after becoming increasingly reclusive - he lost the support of his party and resigned as leader in 1981.
Suarez, however, had one more dramatic moment to play.
About a month after his resignation, during a Parliamentary debate on swearing in a successor, paramilitary Civil Guard police backed by army generals nostalgic for Franco's hard-line rule stormed the ornate chamber in an attempted coup.
When some of the officers started firing submachine guns at the ceiling - the bullets have been left there as a reminder of that day - most lawmakers scrambled for cover, diving to the floor or hiding under the seats. Suarez was one of a handful of politicians who remained seated, upright and defiant. The coup bid soon collapsed.
Suarez ran for election again in 1982 and lost. He eventually formed another centrist party, but it remained marginal and he retired from politics in 1991.
Adolfo, one of Suarez's sons, revealed in 2005 that his father had Alzheimer's disease.
Born September 25, 1932, Suarez studied law at Spain's prestigious Salamanca University and went into politics after graduating.
He held several government posts during the Franco regime.
The king granted him the title of Duke of Suarez in 1981. He was awarded Spain's highly regarded Prince of Asturias prize in 1996 for his contribution to democracy.
Suarez is survived by daughter Sonsoles, a former TV news anchor, and son Adolfo, a politician with the conservative Popular Party, and two other children.
His wife, Amparo Illana, and eldest daughter, Marian Suarez Illana, died of cancer in 2001 and 2004, respectively.