Emergency room doctors are typically called emergency physicians or emergency medicine physicians. In everyday language, people also say “ER doctor” or “ER physician.” These physicians specialize in evaluating and treating acute illness and injury in the emergency department.
According to the American Medical Association, emergency medicine focuses on the quick clinical decisions needed to prevent death or further disability. After medical school, physicians usually complete three to four years of specialty training in emergency medicine before board certification.
Source: Physician specialty: Emergency medicine — American Medical Association (AMA)