The ERS (Entidade Reguladora da Saúde) is Portugal's independent health regulator, responsible for overseeing the quality, access, and safety of healthcare services provided by both public and private providers.

The ERS monitors compliance with patients' rights, investigates complaints, and can issue warnings, recommendations, or sanctions when healthcare standards are not met. It publishes reports on waiting times, diagnostic delays, and access to care that often drive public debate about the state of Portugal's health system.

For residents, the ERS is the body to contact with complaints about healthcare services — whether delays in treatment, quality concerns, or issues with access to the National Health Service (Serviço Nacional de Saúde, SNS) or private providers.