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High-pressure sodium lamps, often abbreviated as HPS lamps, are a type of high-intensity discharge (HID) lamp that produces light by exciting sodium vapor at high pressure inside a quartz or ceramic arc tube. The tube contains sodium, mercury, and often halogen compounds, and is enclosed within an outer bulb. The lamp requires a ballast to regulate current and provide the starting voltage. When energized, an electric arc forms between electrodes, heating the sodium until it vaporizes and emits light.

The light output of HPS lamps is dominated by the sodium emission lines, resulting in a characteristic warm yellow-orange color with high luminous efficacy. Typical color temperatures are around 2,000 to 2,200 kelvin, and the spectral output becomes more continuous at high pressure, improving overall efficiency while giving a distinctive yellowish appearance. Luminous efficacy commonly ranges from about 100 to 150 lumens per watt, depending on design and operating conditions. HPS lamps have relatively long life spans, often tens of thousands of hours, but their light output and color can shift as the lamp ages.

Advantages of high-pressure sodium lamps include high efficiency, good long-term performance, and strong light for outdoor applications. Disadvantages include poor color rendering, especially for color-critical tasks, sensitivity to cycling (on/off switching), and the need for a suitable ballast. They also contain small amounts of mercury and must be disposed of as hazardous waste. In many regions, HPS lighting has been supplemented or replaced by more versatile lighting technologies, such as LEDs, for new installations, though HPS remains in use for certain street, security, and industrial lighting applications.