A highly oriented humic acid film, comprising multiple humic acid (HA) or chemically functionalized humic acid (CHA) sheets that are chemically bonded or merged and are substantially parallel to one another, wherein the film has a thickness from 5 nm to 500 μm, a physical density no less than 1.3 g/cm3, hexagonal carbon planes with an inter-planar spacing d002 of 0.4 nm to 1.3 nm as determined by X-ray diffraction, and a non-carbon element content or oxygen content lower than 5% by weight.