Spanish King Juan Carlos has abdicated in favour of his son Crown Prince Felipe, prime minister Mariano Rajoy announced.
In a televised address, Rajoy thanked the 76-year-old monarch for his role in Spain's transition from dictatorship to democracy.
"His Majesty, King Juan Carlos just announced me his intention to abdicate," Rajoy told the nation this morning. "An historic figure closely bound to Spain's democracy renounces the throne."
The official twitter account of the royal family posted pictures depicting Juan Carlos as he signed his abdication and handed the document to Rajoy.
A series of health problems over recent years are said to be behind Juan Carlos' decision to pass the crown to Prince Felipe.
Juan Carlos came to power in 1975, two days after the death of dictator Francisco Franco.
Rajoy said he is confident the legal formalities necessary for Felipe, 45, to be named King are to be dealt with "in a very short time".
The Prime Minister expressed hopes that what he described as a new page in Spain's history will be written "in a serene atmosphere, with peace and gratitude."
Juan Carlos's popularity with the Spanish public recently dipped following a series of royal scandals, including an elephant-shooting trip he took in the middle of Spain's financial crisis.