Felipe VI of Spain acceded to the throne following the abdication of his father Juan Carlos - the first royal transition since the restoration of Spanish democracy.
The new king received an extended standing ovation from dignitaries in Madrid's Royal Palace as he formally became monarch at midnight on 19 June.
He is the only son of Juan Carlos, and has two elder sisters.
In 2004 he married a star TV presenter, Letizia, and they have two daughters - Leonor and Sofia.
Felipe becomes king at a time when many Spaniards are struggling after years of austerity and economic hardship.
The BBC's Chris Morris in Madrid says he faces the dual challenge of rehabilitating the monarchy damaged by recent scandals, and unifying a country in which a vocal minority favour republicanism.
As crown prince, Felipe assumed many of his father's duties as his health declined in the final years of his reign.
Since 1996 he has represented Spain at the swearing-in ceremonies for presidents in Latin America.
That role has underlined his special interest in relations with Spain's former colonies in the Americas.
In 2011 he performed more royal duties than his father - a total of 253 functions in Spain and abroad.
At the age of 18, in January 1986, he swore allegiance to the monarch and the Spanish constitution.
His full name is Felipe Juan Pablo y Alfonso de Todos los Santos. He is named after Philip V (1683-1746), the first Bourbon king of Spain.
A sports enthusiast, Felipe was in Spain's Olympic yachting team at the Barcelona Games in 1992.
He has a law degree from the Madrid Autonomous University. He graduated in 1993 and went on to spend two years doing a Master's in International Relations at Georgetown University, Washington.
As a school student he had also spent a year at Lakefield College School in Canada.
In 1985-89 he underwent officer training at Spanish military academies. He graduated as a helicopter pilot, lieutenant-colonel in the army and air force and frigate commander in the navy.
Since 2010 he has chaired meetings of the Spanish armed forces chiefs. He also participates in military exercises.
He has travelled to many countries, one of his chief roles being to promote Spanish business interests and culture globally.