BACKGROUND Stroke is an important cause of maternal morbidity and mortality during pregnancy and puerperium. Isolated amnesia is a rare clinical symptom caused by ischemic stroke during pregnancy. We present the first documented case of acute amnesia during pregnancy due to bilateral fornix infarction. METHODS A 32-year-old nullipara presented at 35 wk of gestation with acute amnesia and headache. Brain magnetic resonance imaging and angiography revealed acute infarction in the bilateral anterior fornix. There was no evidence of causative abnormality after extensive work-up, including for vascular abnormality, cardiac disease, coagulopathy, and pregnancy-related conditions. The patient was diagnosed with cryptogenic stroke. Aspirin was administered immediately, and the patient recovered fully without recurrence. CONCLUSIONS Acute isolated amnesia due to stroke is rare during pregnancy. Early diagnosis of stroke and immediate treatment prevent neurologic sequelae.