Background: The respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract illness. Aim of the study: To assess nurses' knowledge about respiratory syncytial virus in emergency unit Research design: Descriptive research design was employed to conduct the study. Setting: The study was conducted at Assiut University's Emergency Departments and the Assiut Chest Hospital. Sample: Convenient sample consisted of 32 nurses were included in the study. Tool: Nurses Knowledge Assessment tool, the tool includes 2 parts Part 1: Emergency Nurse's Socio-Demographic Data. Part 2: Emergency Nurse's Knowledge Questionnaire about RSV Include 30 questions 15 multiple choice question (MCQ) then 15 (False or True ) question on RSV. Results : The findings revealed that (68%) of the nurses surveyed had a good level of knowledge about respiratory syncytial virus. Conclusion: The most of nurses of critical care had good knowledge about respiratory syncytial virus in emergency unit. Recommendation: Encourage additional research about the nurses' role regarding respiratory syncytial virus in emergency units. Orientation and in-service training programs for newly joined nurses in the emergency unit regarding respiratory syncytial virus are needed to increase and Updated nurses' knowledge.