Although Walter E. Dandy (1886-1946) is appropriately credited with the first surgical clipping of an intracranial aneurysm in 1937--a procedure that established the modern field of vascular neurosurgery--his numerous other contributions to this specialty are not as well known. Dandy can be credited with the first detailed description of the vein of Galen malformation, the first description of x-ray visualization of an intracranial aneurysm, the first characterization of basilar artery dolichoectasia, and the publication of the first comprehensive operative case series of arteriovenous malformations, cavernous malformations, and developmental venous anomalies. In addition, Dandy performed the first surgical trapping of a cavernous internal carotid artery (ICA) aneurysm by clipping the supraclinoid ICA and ligating the cervical ICA, and he also executed the first intracranial surgical clipping of the ICA to treat a carotid-cavernous fistula. In this article the authors describe Dandy's contributions to the field of vascular neurosurgery.