Júnior Enrique Díaz Campbell (born 12 September 1983) is a Costa Rican professional footballer who is currently plays for CS Herediano. He plays for the Costa Rica national team. At a top speed of 33.8 km/h, he was deemed by FIFA as the fastest player of the 2014 FIFA World Cup.
Born in Heredia, Costa Rica, Díaz started his career at local side Herediano before moving abroad to join Polish side Wisła Kraków in January 2008. He moved on to Belgian club Club Brugge in September 2010 and was snapped up by German Bundesliga outfit FSV Mainz in summer 2012.
In 2015, after three years in Mainz, Díaz joined Darmstadt 98, a newly promoted team for the 2015–16 season.
Júnior Díaz made his first appearance for the senior Costa Rica national football team in a friendly against China on 7 September 2003. Díaz made one appearance at Copa América 2004, entering as a second-half substitute against Chile. He appeared in all four matches as Costa Rica won the UNCAF Nations Cup 2005 tournament. Díaz also appeared in one match at the 2005 CONCACAF Gold Cup finals.
Díaz was a member of the Costa Rica national football team at the 2004 Olympics in Athens.