A composite of selenium (Se) and a rich porous carbon material (PCM) with mesopores from silk cocoons is explored as a cathode for lithium–selenium (Li–Se) batteries for the first time. Elemental selenium is homogeneously dispersed inside the mesopores of the PCM by a melt-diffusion method based on several analyses. The synthetic PCM/Se composite can effectively suppress the dissolution of the active material and maintain mechanical stability. In the case of Li–Se batteries, it delivers a reversible capacity of more than 230 mA h g⁻¹ after 510 cycles at 2C. The remarkable electrochemical performance may benefit from the favorable conductivity and the porous structure of the carbon material as the host matrix.