Abstract: A lightweight radiation shielding material. A carbon nanotube forest is embedded in a matrix comprising nanoparticulates, such as nanoparticles, carbon nanotubes, or graphene nanosheets. The nanoparticulates can be low atomic number (low-Z) or high atomic number (high-Z). The matrix can be a solidified polymer, epoxy, resin, or ceramic precursor, for example silicon carbide. The radiation shield can shield an object from radio frequency interference (RFI), lightning, electromagnetic interference (EMI), an electromagnetic pulse (EMP), gamma rays, X-rays, neutrons, and/or protons. The nanoforest is disposed on a conductive base with sufficient in-plane electrical conductivity to provide an effective conductive path for currents induced by radiation absorption. The base can be a second nanoforest comprising horizontally-oriented carbon nanotubes, which makes the shield particularly lightweight, as low as 10% of the mass of aluminum that provides equivalent shielding.