Functional oxides are the fundamentals of smart devices. This article reviews novel nanostructures of functional oxides, including nanobelts, nanowires, nanosheets, and nanodiskettes, that have been synthesized in the authors' laboratory. Among the group of ZnO, SnO2, In2O3, Ga2O3, CdO, and PbO2, which belong to crystallo-graphic systems and structures, a generic nanobelt structure has been synthesized. The nanobelts are single crystalline and dislocation-free, and their surfaces are atomically flat. The oxides are semiconductors, and have been used for fabrication of nanodevices such as field-effect transiston and gas sensors. Taking SnO2 and SnO as examples, other types of novel nanostructures are illustrated. Their growth, phase transformation, and stability are discussed. The nanobelts and related nanostructures are a unique group that is likely to have important applications in electronic, optical, sensor, and optoelectronic nanodevices.