In recent years, a lot of controversies have emerged regarding conservative versus liberal oxygen therapy in critically ill patients. While neurologically injured patients might have higher oxygen demand due to high cerebral metabolism, recent studies have clearly shown that hyperoxia may not be beneficial in improving the neurological outcome in traumatic brain injury, subarachnoid hemorrhage, and acute ischemic stroke. Rather, hyperoxia might worsen neurological outcome in such conditions by various mechanisms like direct cerebral vasoconstriction or by increased excitotoxicity, which in turn leads to lipid peroxidation and generation of harmful reactive oxygen species. This article brings into insight the current evidence on the effect of hyperoxia on these three acute neurological insults.