Mauro Zarate scored in the 86th minute to cap Argentina's 2-1 comeback victory over the Czech Republic for a sixth Under-20 World Cup title on Sunday.
Zarate's low shot through traffic from the edge of the penalty box handcuffed goalkeeper Radek Petr.
Sergio Aguero also scored for Argentina in the 62nd, two minutes after Martin Fenin gave the Czechs a 1-0 lead in the final.
The South Americans have won five of the last seven tournaments, and six of the 16 U20 tournaments overall — in 1979, 1995, 1997, 2001, 2005 and now 2007. They have reached the semifinals eight times in twelve attempts, and six times in their last seven appearances.
Reaching the final was the Czechs' best effort.
Aguero was named winner of the Golden Boot as tournament top scorer with six goals. He also won the Golden Ball as best player in a vote of the media, ahead of Argentina's Maximiliano Moralez and Mexico's Giovani Dos Santos.
Aguero, who went on as a substitute in the 2005 final against Nigeria, became only the second player to play on the winning side in two U20 finals. Portugal's Jaoa Pinto also did it in 1989 and 1991.
Earlier, Chile defeated Austria 1-0 to finish in third place, ending the tournament on a happier note than the post-game brawl that followed its semifinal loss to Argentina on Thursday.