Well barriers is a research concept and engineering discipline focused on the design, implementation, and integrity management of redundant physical or operational controls within a wellbore system. It investigates the principles and methodologies required to prevent the unintended flow of reservoir fluids or injection fluids into the environment or other formations, ensuring containment and operational safety. Key characteristics include the requirement for multiple, independent layers of protection, each capable of preventing uncontrolled flow, and the systematic assessment and verification of their integrity throughout the well's lifecycle. Its significance lies in its critical role in safeguarding personnel, protecting the environment, and enabling safe and controlled resource extraction or subsurface utilization.