The concept of a super critical-pressure, direct-cycle light water reactor is presented. Its feasibility is assessed by a study of its neutronic and thermal-hydraulic design. The system pressure is 250 bars. The coolant density decreases continuously in the core, and the coolant is fed directly to the turbines. This eliminates the recirculation system, steam separators, and dryers. The diameter of the reactor pressure vessel is smaller than that of a pressurized water reactor (PWR), and the vessel wall is not very thick despite the high pressure. The required core flow rate is about one-eighth that of a PWR. There are only two coolant loops in a 1145-MW(electric) reactor, and the turbines are smaller than those of a light water reactor. These features greatly simplify the reactor plant. The thermal efficiency is improved 19% over that of a PWR.