Aneurysmal subarachnoid haemorrhage (aSAH) is bleeding into the subarachnoid space from a ruptured intracranial aneurysm, the cause of most non-traumatic subarachnoid haemorrhage. Rupture causes early brain injury and exposes the patient to rebleeding, hydrocephalus and systemic complications. It presents with sudden severe headache, often with reduced consciousness; early CT is highly sensitive, lumbar puncture covers late presentation or persisting doubt, and CT angiography finds most aneurysms. Management secures the aneurysm early, by coiling in patients in good clinical condition whose aneurysm suits both coiling and clipping, alongside neurocritical care, nimodipine and drainage of hydrocephalus; routine tranexamic acid is not recommended. A joint European Stroke Organisation (ESO), neurosurgical and neurointerventional guideline frames European practice.