Abstract: Polymer-derived, graphene reinforced ceramic matrix composites and processes for producing graphene-ceramic ceramic matrix composites are provided. An example process mechanically delaminates graphite mixed in a thermosettable, liquid preceramic polymer through a mechanical, high shear process to generate a composition of a preceramic polymer in which graphene is homogeneously dispersed. This example process does not require high temperatures and pressures to produce the graphene. The resulting composition can be pyrolytically converted to a graphene-reinforced ceramic matrix composite. A polysilazane can be used as the preceramic polymer, in some cases providing ammonia or an amine in the process to facilitate delamination of the graphite to graphene. Ceramic, metal, mineral or carbon particulates, platelets, or fibers may be added to the composition to impart enhanced mechanical and/or electrical properties to the finished graphene-reinforced ceramic matrix composites.