MgAl2O4 spinel nanowires have been synthesized on an alumina substrate by reaction of magnesium oxide powders with graphite at 1350 °C in a flowing argon atmosphere. Transmission electron microscopy (TEM) images show that they have a diameter of 50–120 nm, and a length up to 500 micrometers. Meanwhile, coaxial nanostructures of spinel nanowires sheathed with alumina have been discovered. The growth process of the nanowires may be explained by a vapor–liquid–solid mechanism of bottom growth.