Left main coronary artery aneurysms are very infrequent (0.1%) and the majority is related to atherosclerotic obstructive lesions. We describe a young male having no conventional coronary risk factors presenting with acute inferior wall myocardial infarction. Coronary angiography revealed a prominent aneurysm of the left main coronary artery with selective extension towards the proximal left circumflex artery without associated coronary lesions.