Sunglasses or sun glasses are a visual aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to prevent strong light from reaching the eyes. In the early Twentieth century they were also known as sun cheaters (or simply cheaters).

Many people find direct sunlight too bright to be comfortable. 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, which can lead to the development of a cataract. Sunglasses have also been associated with celebrities and film actors primarily due to the desire to hide or mask their identity, but this may also be due in part to the fact that film lighting is typically stronger than natural light and uncomfortable to an unprotected eye. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.