Selenium/carbon-rich (Se/carbon-rich) core–shell composites are prepared by a one-step hydrothermal synthesis method as a cathode for rechargeable lithium batteries. The Se/carbon-rich composites are characterized and examined by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetry (TGA) measurements. It is demonstrated from galvanostatic discharge/charge process that the Se/carbon-rich composites exhibit the discharge capacity of 558 mA h g−1 in the first cycle and maintain capacity of 181 mA h g−1 after 80 cycles at a rate of 0.5C, which is better than that of the pristine selenium. The result demonstrates that the unique core–shell structure is effective in suppressing the dissolution of polyselenides into the electrolyte and in maintaining high utilization of the active materials during the charge/discharge process. It provides a new selenium-based cathode material for rechargeable lithium batteries.