The ability to control the morphology of fluorite-structured cerium oxide nanomaterials is an important step in the design of cerium oxide-based catalysts. Herein, we report an additive-free synthesis of cerium oxide nanorods with highly tunable aspect ratios from similar to 6:1 to 40:1. The use of a microwave hydrothermal method allows for both rapid synthesis and temperature control. The ability to control the length of the nanorods from <51nm to >1.7m by varying only the reaction temperature was demonstrated over a temperature range of 80 degrees C to 200 degrees C. The formation of the resulting nanorods was investigated using selected-area electron-diffraction and high-resolution transmission electron microscopy. The surface area of nanorod products was found to decrease from 117 to 22m(2)/g as the reaction temperature increased from 80 degrees C to 200 degrees C, complementing the general trend of the increasing aspect ratios of these products.