John Mercado is an Ecuadorian winger born in Guayaquil on 3 June 2002. After early development with Clan Juvenil, Panamá and Athletico Paranaense, he made his professional debut in Brazil and had a loan spell with CSA. Mercado then moved to Portugal, playing for Vilafranquense and AVS, before signing for Sparta Prague in August 2025. He represented Ecuador at under-15, under-17 and under-20 levels, including the 2019 FIFA U-17 World Cup. Mercado made his senior Ecuador debut in September 2024 in a World Cup qualifier against Brazil.