Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible lightfrom damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glassesexist which feature lenses that are colored, polarized or darkened. In the early 20th century they were also known as sun cheaters(cheaters being an American slang term for glasses).

Many people find direct sunlight too bright for comfort. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation and blue light, which can cause several serious eye problems. Sunglasses have long been associated with celebrities and film actors primarily from a desire to mask their identity. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.