A clear majority of Spaniards have voted in favour of the European Union constitution in a referendum.
Most Spaniards admit they have little idea about the EU constitution
The blueprint for the EU's future was backed by 77% of voters, with 17% against, official figures showed.
Spain's prime minister hailed the result, but his opponents pointed to the low turnout of 42%.
It was the first of a series of European polls on the constitutional treaty, which must be ratified by all 25 EU member states to go into effect.
The deadline for ratification is November 2006.
Prime Minister Jose Luis Rodriguez Zapatero told reporters: "Today has been a great day for all Europeans".
European Commission President Jose Manuel Barroso, who called Mr Zapatero to congratulate him, welcomed "the very clear 'yes' which Spain has given to a Europe which moves forward and which makes a difference, a Europe united in diversity".
The EU constitution is designed to streamline the EU's decision-making process after the bloc brought in 10 new members - mostly from central and eastern Europe - last May.
The BBC's Katya Adler, in Madrid, says the turnout was embarrassingly low for the Spanish prime minister, who had promised to set a shining example for the rest of Europe.
Critics said the government's information campaign had been glitzy - with football and film stars calling for a Yes - but did not do enough to inform voters about the content of the charter.
In a recent poll, nine out of 10 Spaniards admitted they had little idea what the EU constitution is about.
The referendum was non-binding, with parliament set to have the final say.
Voters were asked: "Do you approve the treaty establishing a constitution for Europe?"
Early voters in Madrid included King Juan Carlos, who cast his ballot at a school.
The EU constitution provides for the first EU president and foreign minister and incorporates certain fundamental rights into EU law.
Nine EU members have definitely said they will hold referendums, with two more countries undecided. The remainder are ratifying the treaty by a parliamentary vote.
Spain joined the EU in 1986, and has since benefited from generous EU subsidies.