Sunglasses (also called sun spectacles – see usage of words for eyepieces) are a kind of visual correction aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to screen out strong light from the eyes.

Many people find direct sunlight too bright to be comfortable, especially when reading from paper on which the sun directly shines. Also, with the rise of the atmosphere's damaged ozone layer, it has been recommended to the public to wear these kind of glasses on sunny days to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have also been associated with film actors since the lighting involved in production is typically strong and uncomfortable to the naked eye.

It is important to ensure that the makers of one's sunglasses ensure that the glasses protect against UV rays. Lenses that are simply dark but do not provide UV protection may actually make things worse, as the dimmer light causes the pupils to dilate, admitting more UV rays.

Corrective lenses can be darkened to serve the same purpose, or secondary clip-on dark lenses can be placed in front of the regular lenses.

People with severe visual impairment, such as the blind, often wear sunglasses so they do not make others uncomfortable with the fact that they cannot make eye contact with them (not seeing eyes may be better than seeing eyes which seem to look in the wrong direction), or to hide the eyes if their appearance is abnormal, for example due to cataracts. Some people who are severely visually impaired but still sighted wear sunglasses in order to protect their vision against glare.

Sunglasses were first used in China in the 12th century or possibly earlier. The "lenses" of these glasses were flat panes of smoky quartz, which offered no corrective powers but did protect the eyes from glare, and, according to some sources, evil spirits. Contemporary documents describe the use of such glasses by judges in Chinese courts to conceal their facial expressions while questioning witnesses.

James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern of his.

Sunglasses as such were introduced by Sam Foster in 1929. Foster found a ready market on the beaches of Atlantic City, New Jersey, where he began selling Foster Grants from a Woolworth on the Boardwalk .

Sunglasses would not become polarized, however, until 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.

In 2004 Oakley (fashion) has developed Thump, sunglasses with built-in MP3 player.

People predominantly seen wearing sunglasses

Some celebrities are predominantly seen in public wearing sunglasses. These people include:

• Bono
• Habib Bourguiba
• Ray Charles
• Tom Clancy
• Elton John
• Bootsy Collins
• James Dean
• Magenta De Vine
• Andrew Eldritch (of The Sisters of Mercy)
• Gnassingbe Eyadema
• Jose Feliciano
• Billy Gibbons (of ZZ Top)
• Heino (German singer)
• Dusty Hill (also of ZZ Top)
• Wojciech Jaruzelski
• Jackie Kennedy
• Karl Lagerfeld
• John Lennon - often wore sunglasses with distinctive perfectly round lenses.
• Jeff Lynne (of Electric Light Orchestra)
• Clayton Moore, The Lone Ranger
• Jack Nicholson
• Yoko Ono
• Roy Orbison
• Richard Petty
• Pat Rice (Arsenal football (soccer) coach)
• Julien Roche
• Stevie Wonder
• Pedro Abrunhosa
• Eric Williams

The reasons for this are varied and the behavior is typically the source of much speculation in the yellow press.

Fictional characters predominantly seen wearing sunglasses

Some fictional characters are predominantly depicted as wearing sunglasses. These include:

• The Blues Brothers
• Cliff, the troll "rock" musician in Soul Music
• "Joe Cool", Snoopy's alter-ego
• The Corinthian, from The Sandman (DC Comics Modern Age)
• Crowley, from Good Omens
• Cyclops, from the X-Men - wears sunglasses when he is not in costume with his visor
• Iggy, from Hey Arnold!
• The Men in Black
• Numbuh One (Nigel), from Codename: Kids Next Door
• Riff from Sluggy Freelance
• Otto, from Rocket Power
• Sparky the Penguin from This Modern World comic strip
• The Terminator
• Most characters from The Matrix movie. Interestingly, all of the protagonists wear rounded lenses, while the antagonists wear rectangular lenses