Patient safety refers to the prevention of avoidable harm to patients during healthcare delivery and the reduction of unnecessary risks associated with diagnosis, treatment, medication, surgery, infection control, and other healthcare processes. It is an essential component of quality healthcare because even when healthcare professionals possess adequate knowledge and skills, unsafe systems, communication failures, human errors, equipment problems, and organizational weaknesses can result in patient injury or death. Patient safety is therefore not only the responsibility of an individual healthcare worker but also a responsibility of healthcare organizations, managers, policymakers, and the healthcare system as a whole. The need for patient safety arises from the complex nature of modern healthcare. Patients may undergo multiple investigations, receive several medicines, interact with different healthcare professionals, and move between departments or institutions. Every transition creates opportunities for errors. Common preventable adverse events include medication errors, wrong-patient or wrong-site procedures, healthcare-associated infections, falls, pressure injuries, diagnostic errors, transfusion errors, surgical complications, and failures in communication. Such incidents can lead to prolonged hospitalization, disability, psychological suffering, increased healthcare costs, loss of income, and sometimes death. Patient safety is also closely related to worker safety. Healthcare workers operate in environments where they may be exposed to infectious diseases, sharps injuries, hazardous chemicals, radiation, violence, ergonomic hazards, and psychological stress. A safe working environment helps workers provide safer care. For example, appropriate sharps disposal protects both patients and healthcare workers from blood-borne infections. Adequate staffing, proper training, personal protective equipment, infection prevention practices, and safe equipment reduce risks for everyone in the healthcare environment. Another important reason for emphasizing patient safety is the ethical principle of non-maleficence, which requires healthcare professionals to avoid causing harm. Patients trust healthcare professionals and institutions with their lives and wellbeing. Healthcare providers therefore have an ethical and professional obligation to identify risks, prevent avoidable errors, disclose adverse events appropriately, and continuously improve the quality of care. Patient safety also supports the principles of beneficence, respect for patients, informed decision-making, and patient-centred care. Unsafe care has considerable economic consequences. Preventable adverse events may require additional treatment, investigations, medicines, surgery, rehabilitation, or prolonged hospital stays. They increase the financial burden on patients, families, hospitals, and health systems. Effective patient-safety programmes can reduce these costs by preventing errors and complications before they occur. Safety improvement is therefore both a clinical and an economic priority. The development of patient safety as a major field has occurred gradually through several important milestones. Early healthcare systems primarily focused on the competence and responsibility of individual professionals. Errors were often considered individual failures, and there was limited systematic investigation of adverse events. Over time, the understanding developed that many errors arise from weaknesses in healthcare systems rather than from individual negligence alone. One of the earliest important milestones was the development of organized hospital quality-improvement activities during the twentieth century. The establishment of professional standards, accreditation systems, medical audits, nursing standards, and quality assurance programmes created mechanisms for monitoring healthcare performance. The Joint Commission and similar accreditation organizations contributed to the development of systematic approaches to healthcare quality and safety. A major milestone was the publication of studies demonstrating