Two methods are described for the production of bulk nanostuctured ceramics: one for single phase ceramics and the other for multi-phase ceramics. The first method makes use of a metastable nano-scale powder as starting material and pressure-assisted sintering to develop a nanocrystalline product. The second method utilizes a metastable micron-scale powder as starting material and pressure-assisted sintering to develop a nanocomposite product. Both methods depend for their success on control of a pressure-induced phase transformation to promote rapid densification without causing significant grain growth. Several examples are given to illustrate the versatility of the transformation-assisted consolidation process.