Acute pelvic pain in women is a common reason for emergency department admission. There is a broad range of possible aetiological diagnoses, with gynaecological and gastrointestinal causes being the most frequently encountered. Gynaecological causes include upper genital tract infection and three types of surgical emergency, namely ectopic pregnancy, adnexal torsion, and haemorrhagic ovarian cyst rupture. The main gastrointestinal cause is acute appendicitis, which is the primary differential diagnosis for acute pelvic pain of gynaecological origin. The process of diagnosis will be guided by the clinical examination, laboratory study results, and ultrasonography findings, with suprapubic transvaginal pelvic ultrasonography as the first-line examination in this young population, and potentially cross-sectional imaging findings (computed tomography and MR imaging) if diagnosis remains uncertain.