National Dark Sky Week is an event in the United States which is designed to draw people's attention to the issue of light pollution. It was founded in 2003 by Jennifer Barlow, an astronomy enthusiast who was frustrated by poor observing conditions caused by light pollution. A number of astronomy organizations have endorsed National Dark Sky Week and encouraged people to take part. Participation is not, of course, limited to Americans: people all over the world are welcome to think about the issue of light pollution and take steps to combat it.

As the name implies, the primary goal of National Dark Sky Week is to get people to turn off unnecessary lights, especially outdoor lights, for a week. Participants are also encouraged to lower the wattage of outdoor lights and aim such lights more efficiently. The hope is that by doing this for a week, people will consciously think about light pollution, and the changes they make in their lives for National Dark Sky Week might be internalized.

By turning their lights out, participants in National Dark Sky Week will be better able to see the sky and the stars. For astronomers, light pollution is a serious problem which makes it difficult to make observations and to enjoy the night sky, and many astronomers worry that light pollution has created a disconnection between people and the stars. This annual event is designed to remind people that the universe is out there, and that the night sky holds a number of interesting sights. Many astronomy organizations organize observing sessions during National Dark Sky Week to encourage people to get outdoors at night and see the wonders of the night sky.

National Dark Sky Week also draws attention to the issues associated with light pollution. Light pollution doesn't just infuriate astronomers: it also disrupts sleep patterns, disturbs wildlife, and wastes copious amounts of energy. Promoters of National Dark Sky Week point out that by turning off unnecessary lights, people will save a substantial amount of energy, and if people keep an energy-efficient mentality in mind all year, they can save a lot of money.

To improve visibility, National Dark Sky Week always takes place during the week of the new moon, and it typically occurs in April. In 2008, the organizers coordinated National Dark Sky Week with Earth Hour, an event where everyone around the world is asked to turn the lights out for an hour. Many cities participated in Earth Hour, extinguishing the lights on famous landmarks from the Sydney Opera House to the Golden Gate Bridge.

The organizers of National Dark Sky Week would like to remind participants that the goal is to turn of unnecessary lights. Lights which are necessary for safety should be left on, although the group hopes that participants consider energy efficient safety lights such as lights with shields which aim the light precisely where it is needed, and lights with motion detectors which remain off when they are not needed.