Abstract Carbon‐doped fused silica glass is fabricated by consolidating zinc stearate‐doped porous silica soot blank. The carbon doping concentration is tunable and a maximum of ~0.3 wt% carbon can be incorporated into densified silica. Carbon dopants assemble into nanorod structures which are uniformly distributed inside glass. Transmission electron microscopy electron energy loss spectroscopy and Raman studies identify that carbon dopants are a mixture of nanosized silicon carbide and multiple layer graphene, which produce strong and flat optical absorption in a wide wavelength range of 400‐2500 nm. The electrical resistivity of silica glass is reduced by about 15 orders of magnitude with 0.28 wt% carbon doping.