A lightweight, high strength carbon aerogel composite and method of producing such a composite. An organic gel precursor is infiltrated into a pre-formed organic polymer foam or fiber-mat where it gels. The gel composite is then dried by any method that limits the shrinkage of the composite material. The dried gel is then heated in a furnace to pyrolyze the composite, reducing it to a glassy carbon form. The structure of the final carbon product consists of a matrix of porous carbon aerogel, reinforced by solid carbon struts, or fibers all in intimate contact, so that the strength of the composite is maximized.
 The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.