Surveillance plays a crucial role in improving population health. Public health surveillance systems generate information that guides action, and the data collected must adhere to quality standards, with appropriate detail and timeliness to meet specific objectives. Given the advancements in public health surveillance, changes in healthcare and public health landscapes, and the rapid development of new technologies, this chapter aims to examine these surveillance systems. We will explore their current applications in enhancing the efficiency and effectiveness of the public health system, the roles of various stakeholders, the analysis and interpretation of surveillance data, methods for monitoring and evaluating these systems, and potential future developments that focus on increasing scientific rigor, outcomes-based research, and health informatics.