The 18-year-old Spaniard defeated Ruud 7-5, 6-4 at Hard Rock Stadium in the American city to seal his first Association of Tennis Professionals (ATP) Masters 1000 title.

Alcaraz replaced Novak Djokovic as the youngest winner of the men’s singles crown in Miami, with the Serbian taking the title in 2007 at the age of 19, and he became the third-youngest ATP Masters 1000 champion.

Only Michael Chang of the United States in 1990 and Spain’s Rafael Nadal in 2005 were younger than Alcaraz's 18 years and 333 days when they won their first respective ATP Masters 1000 titles.

"I have no words to describe how I feel right now," said Alcaraz who is set to rise to a career-high world number 11.

"It's so special to win my first Masters 1000 here in Miami.

"I have an unbelievable team with me and family.

"I'm so happy with the win and my team."

Ruud, competing in his 10th ATP Tour final, was seeking the second hard-court trophy of his career and got off to a fine start against Alcaraz.

The Norwegian led 4-1 as Alcaraz took time to settle before winning six of the next seven games to take the opening set.

Alcaraz then turned on the style with a pair of winners to seal his two early breaks in the second.

Ruud got one break and then held to love before taking a medical timeout to receive treatment for an issue with his left hip.

Alcaraz backed up blistering groundstrokes with strong serving as he dropped just two points in his final three service games, including two love holds.

He sealed the title with a serve and volley before collapsing to the court in celebration, becoming the first Spaniard to claim the men’s singles crown following eight previous final appearances.

"I knew that Casper is playing unbelievable," said Alcaraz.

"He has a big forehand.

"I tried to play to his backhand first and attack all the time.

"I tried not to let him dominate the match.

"Forehand down the line, backhand down the line was a pretty good key for me."

Laura Siegemund and Vera Zvonareva stunned top seeds Veronika Kudermetova and Elise Mertens 7-6, 7-5 to win the women’s doubles title in Miami.

The match featured two Russians with Zvonareva and Kudermetova competing as neutrals due to sanctions imposed by tennis authorities against Russia over the war in Ukraine.

Zvonareva got the better of her compatriot as she and Germany’s Siegemund fought back from a break down in each set before gritting out the win against Kudermetova and Belgium’s Mertens.