Esporte Clube Agua Santa, commonly referred to as simply Agua Santa, is a Brazilian association football club in Diadema, Sao Paulo, currently playing in the Paulistao, the top tier of the Sao Paulo state football league.
Founded as an amateur team by migrants on 1981, Agua Santa became one of the strongest non-professional teams in the ABC region, winning 17 titles during that time. On 8 December 2011, the team turned pro, joining the Campeonato Paulista Segunda Divisao in 2013. Agua Santa won three consecutive promotions in their first years of professionalism, and by 2016, they were already in the top tier of the Campeonato Paulista. They were relegated back to Campeonato Paulista Serie A2 after just one season in the top flight. They were promoted to the first division again for the 2020 season, were relegated again in the same year, and won promotion back to the top tier in the following season.
Since the beginning of the professional era, Agua Santa has played at Estadio Municipal Jose Batista Pereira Fernandes, better known as Arena Inamar. The club's home colours are white and blue and the team mascot is Neptune, the roman god of the sea. Their main rivals are Sao Bernardo, Sao Caetano and Santo Andre. Agua Santa also had a troublesome off-field relationship with cross-town rivals Clube Atletico Diadema, which resulted in the latter team leaving for Ribeirao Pires.