MADRID, Spain (CNN) -- After nearly 40 years on the throne, King Juan Carlos I of Spain will be stepping down, the country's prime minister said Monday.
Crown Prince Felipe, 46, will succeed his father, Prime Minister Mariano Rajoy announced in nationally televised address.
Rajoy did not offer a reason for the king's planned abdication. The king is expected to issue a statement later Monday.
Spaniards generally hold Juan Carlos, 76, in high regard for his service to the nation and his defense of democracy after the death of the dictator Francisco Franco in 1975.
But the king's popularity took a hit in 2012 over a controversial elephant-hunting trip to Africa while the nation was mired in a deep economic crisis.
The focus of his reign was to bring about reconciliation between Spaniards of different political persuasions, and from different regions.
Many consider the the king's finest hour to be his decisive stand to halt a right-wing military coup in 1981, when he went on television to say that the monarchy would not tolerate attempts to interrupt democracy by force.
Oversaw democracy's return
Born in Rome in 1938, Juan Carlos didn't set foot in Spain until he was 10. In Franco's Spain, he carried out military training and became the first Spanish officer to hold the rank of lieutenant in all three branches of the military.
In 1969, he was invested as Crown Prince and the designated successor to Franco.
On November 22, 1975 -- two days after Franco's death -- Juan Carlos was crowned King of Spain, restoring the monarchy after a 44-year interregnum.
In 1977, he enacted political reforms that led to Spain's first democratic election since 1936.
During his reign, Spain grew into an economic powerhouse and a vacation playground for Europe.
The King and Queen Sofia had three children and numerous grandchildren, styling their monarchy as accessible and relatively austere.
Hunting trip dented image
The private trip to Botswana only became public after Juan Carlos fell, broke his hip and was rushed back to Madrid for surgery.
With millions of Spaniards unemployed, the expense of the African trip caused an outcry. That prompted the king made a rare apology in which he said he had made a mistake which would not happen again.
The king had previously expressed his concern over the impact of the crisis on Spaniards and called on the nation to come together to get through the tough times.
CNN's Al Goodman reported from Madrid; Jethro Mullen wrote from Hong Kong
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