Ectopic pregnancy is the implantation of a fertilized egg outside the uterine endometrial cavity. For women presenting to the emergency department with abdominal pain and/or vaginal bleeding, ectopic pregnancy is an important diagnostic consideration. The diagnosis is made based on laboratory values and ultrasound imaging findings. The ultrasound appearance of both normal early pregnancy and ectopic pregnancy are variable and often subtle, presenting diagnostic challenges for radiologists. This pictorial essay describes and illustrates the sonographic findings of ectopic pregnancy and reviews the differential diagnoses that can mimic ectopic pregnancy on ultrasound. With the possibility of medical management, the value of early detection and prompt initiation of treatment has increased in improving clinical outcomes and preventing the complications of ectopic pregnancy.