Real Madrid became the first team to win back-to-back Club World Cup titles as Cristiano Ronaldo's second-half free-kick beat Brazilian side Gremio.
Zinedine Zidane's side dominated from the start but found chances difficult against the well-organised opposition.
But Ronaldo got the breakthrough with a well-struck effort from 25 yards.
It is a record-equalling third Club World Cup win for Real, who also triumphed in 2014, matching Barcelona's achievement.