Spain's King Juan Carlos said he is abdicating to "ensure stability" in the country.
In a televised statement, he said: "My son [Crown Prince] Felipe, who is the heir to the throne, is the incarnation of stability.
"When I turned 76 in January, I decided it was the moment to prepare passing the baton to someone who can ensure stability".
He ended the broadcast with the words: "I will always hold Spain in the depths of my heart".
More top news
Questions on Russia and Syria are sure to dominate Defence Secretary Michael Fallon's meeting with his US counterpart Ash Carter.
Smoking could kill two million Chinese in 2030 with the country facing a "growing epidemic of premature death from tobacco".
A great-great-great-grandmother has become an unlikely star at the age of 93 after her grandson shared a video of her dancing to rap music.