Magnesium borate nanobelts have been prepared by heating mixed powders of boron and MgO under flowing Ar/H2O gases at 1100 degrees C. Typical widths with the nanobelts are in the range of 100-300 nm and lengths are up to tens of micrometers. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns show the nanobelts are of orthorhombic Mg3B2O6 structure. Furthermore, high-resolution transmission electron microscopy (HRTEM) identifies that the magnesium borate nanobelts are single crystalline in nature. The mechanism for the formation of magnesium borate nanobelts has been primarily presented. (c) 2005 Elsevier B.V. All rights reserved.