The youngest to play in a world cup and win it is the great Pele, from Brazil, he was 17 years old.
Pele
Pele
James O'Connor from Australia who kicked 5 penalties in their first match so hes the youngest rugby player to play in the world cup.
Gulam
It was Michael Owen.
It is sachin Tendulkar.
It could be Pele he was 17 years in 1958 world cup in Sweden.
Talha Jubair (Bangladesh) is the youngest player to play world cup cricket match. He was 17 years and 70 days in 2003 Cricket World Cup to play for Bangladesh
Ricardo Gardner.
It was Pele at 17 years.
Samuel eto'o fils