Emergency medicine is the medical specialty that treats illnesses or injuries requiring immediate medical attention. Emergency physicians (often called “ER doctors” in the United States) continuously learn to care for unscheduled and undifferentiated patients of all ages. As first-line providers, in coordination with Emergency Medical Services, they are primarily responsible for initiating resuscitation and stabilization and performing the initial investigations and interventions necessary to diagnose and treat illnesses or injuries in the acute phase. Emergency physicians generally practice in hospital emergency departments, pre-hospital settings via emergency medical services, and intensive care units. Still, they may also work in primary care settings such as urgent care clinics.

Sub-specializations of emergency medicine include; disaster medicine, medical toxicology, point-of-care ultrasonography, critical care medicine, emergency medical services, hyperbaric medicine, sports medicine, palliative care, and aerospace medicine.

Various models for emergency medicine exist internationally. In countries following the Anglo-American model, emergency medicine initially consisted of surgeons, general practitioners, and other generalist physicians.