King Felipe VI and the royal family met the Spanish delegation, led by captain Rodri and coach Luis de la Fuente, at Zarzuela Palace before the players continue their journey into the city with a million fans expected to celebrate with them.
"You have shown your grit, your resilience and your courage, always backed by your technical skill, your control and command of the game, combining head and heart," the king told La Roja's stars, who were dressed in suits.
Spain beat Argentina on Sunday in extra time thanks to Ferran Torres' strike to clinch their second World Cup, following a first victory in 2010.
The king was joined by Queen Letizia, who wore a red dress to match the colour of the Spanish team's jerseys, and their two daughters, Princess Leonor and Princess Sofia.
Felipe greeted and shook hands with each player, leaning in for a hug with Barcelona's teenage sensation Lamine Yamal.
The king told the players they had been "united" on their "odyssey" to win the expanded 48-team tournament.
The squad then met Prime Minister Pedro Sanchez at his Moncloa residence before an open-top bus parade through central Madrid, where large crowds in national team colours had already gathered.
Spain captain Rodri held the World Cup trophy aloft at the top of the stairs as he descended from the Iberia plane that flew the team home after clinching their second star.
At Moncloa, Manchester City midfielder Rodri said this was the crowning achievement of his career.
"I've always said it, winning with your country is the most beautiful thing there is, above all a World Cup," said Rodri.
"This generation grew up watching (Iker) Casillas and (Andres) Iniesta lift the cup and that we can do it today is the biggest thing you can do in football."
Many younger supporters were not yet born when Andres Iniesta's extra-time goal against the Netherlands secured Spain's first World Cup in South Africa 16 years ago.
Match-winner Torres joked he was "flying, literally" after the team returned from the United States after beating Argentina in New Jersey.
"I'm very happy to see how excited all of the children are... (and) to have the parade and celebrate with all of the Spaniards," he added.
On Monday morning, the Castellana, Madrid's main avenue, bore the marks of a boozy evening -- the tarmac strewn with trash, beer cans and shards of glass.
Among the last remaining supporters, some slept with grins on their faces on the pavement or on benches, while others were still staggering home as cleaning crews worked from the early hours to prepare the route for tonight's party.
Spain's World Cup winners' bus parade starts at Moncloa before heading to Cibeles square. A ceremony involving the players will then be held at the square, the traditional gathering point for celebrations by the Spanish national team and its supporters.
Some fans, who already had only a short night's sleep, are planning to celebrate again, like Bruno Gonzalez del Yerro, a 32-year-old financier.
"We'll have to celebrate it one way or another, given that it only happens every four years and that Spain hadn't won it for about (sixteen) years now -- it definitely deserves a party," he said.
Both trophies
Spain's women's side won the World Cup in 2023, meaning for the first time a country has both trophies at the same time.
In 2030, Spain will defend their crown on home soil, as one of the World Cup hosts along with Portugal and Morocco.
"It's two for two," said Prime Minister Sanchez, of Spain's record in World Cup finals. "Why not dream of a third in 2030, especially with Spain as hosts?"
The Spanish press was running out of superlatives to describe its heroes after they overcame favourites France in the semi-finals before downing Argentina.
"The kings of all-time!" wrote Marca, celebrating a "second star that will now be stitched onto the Spanish jersey after yet another masterclass in collective play."
Argentina, despite the presence of all-time great Lionel Messi, failed to create clear chances against Spain's well-organised and more positive side in the final.
Messi had a sensational World Cup but drifted through the final like a ghost, shedding tears at the end. In Madrid, tears will also flow on Monday night, but tears of joy.
FIFA World Cup 2026
The 2026 World Cup took place from June 11th to July 19th in the United States, Canada and Mexico. The tournament featured 48 national teams and was won by Spain, who beat Argentina in the final.
Full schedule and results | Group standings and bracket | Past winners of the tournament | Our team of the tournament | About the 2030 World Cup