The European champions controlled possession for much of the contest but were repeatedly frustrated by Argentina s disciplined defence and an inspired performance from goalkeeper Emiliano Martinez, who produced a series of crucial saves to keep his side in the match.
The turning point came deep into second-half stoppage time when Argentina midfielder Enzo Fernandez was shown a second yellow card after a reckless challenge on Pau Cubarsi, reducing the defending champions to 10 men.
Spain maintained relentless pressure in extra time against Argentina s deep defensive block before finally breaking the deadlock early in the second period.
Substitute Ferran Torres latched onto a clever knock-back from Nico Williams and calmly slotted home the winner to hand Spain the world title.
Managed by Luis de la Fuente, Spain built their triumph on defensive solidity, conceding just one goal in seven matches throughout the tournament while dominating opponents with their trademark possession-based style.
Argentina, led by veteran Lionel Messi, produced a resilient campaign, surviving a dramatic knockout run that included a comeback victory over Egypt and a 2-1 win against England in the semi-finals before falling agonisingly short in the final.
