The x-ray windows herein can have low gas permeability, low outgassing, high strength, low visible and infrared light transmission, high x-ray flux, low atomic number materials, corrosion resistance, high reliability, and low-cost. The x-ray window can include a film 11 with a polymer layer 22 and a graphite layer 21. The film 11 can consist essentially of graphite and polymer. Most of the film 11 can be the graphite layer 21. The polymer layer 22 can be a small portion of the film 11.