Dark infrastructure refers to interconnected networks of natural, semi-natural and urbanized spaces, characterized by low levels of artificial light at night (ALAN), that create ecological continuities in order to provide benefits such as ecological restoration, wildlife conservation, and human health. Dark infrastructure aims to recognize the need for natural periods of darkness for life on Earth.

In practice, different levels of administrative agencies assess, upgrade and monitor existing areas where the environment remains sufficiently undisturbed light-wise for biodiversity to prosper. Modeled on and complementary to ecological infrastructure networks, dark infrastructure most often consists of cores of darkness connected through corridors. They are expected to sustain human and wildlife health as well as maintain ecosystem services in urban areas.

Some cities and regions (e.g. Trame noire, Eurométropole Metz) in France, Switzerland (e.g. Trame noire and Plan Lumière, Geneva) and the United States have adopted this approach. Some cities in Normandie have since rescinded their plan.

Several western countries have seen the emergence of dark-sky movements, which focus on the human benefits of experiencing starry night skies.

The rationale is that since the Industrial Revolution, the intensity and area of artificially lit outdoor spaces has increased dramatically worldwide, disrupting natural cycles and circadian rhythms of humans and animals alike. The effects of ALAN on wildlife, human health, ecosystem services and biodiversity are widespread and severe. Through the Avoiding Barrier effect for terrestrial mammals and amphibians and the Sink/Crash barrier effect for insects and possibly birds, ALAN can further amplify habitat loss and fragmentation for many organisms.

Light pollution or ALAN is known to cause harm to humans, flora and fauna alike.

For humans, this includes adverse effects on the visual system and sleep quality (e.g., by an impaired melatonin secretion, disruption of the circadian rhythm). Early-stage research also links ALAN to a higher risk of chronic diseases.

ALAN has been linked as one of the causes of the collapse of insect populations which is happening around the world. The skyglow caused by ALAN can sometimes cover areas of over ten to hundreds of kilometers, even affecting animals in unpopulated areas and protected habitats. One problem of the additional light exposure during the night is the disruption of the circadian rhythm and associated risks similar to humans. Another issue arising from ALAN for animals in the sense that lit areas act as barriers that some animals cannot cross. They either avoid the light barrier altogether (bats, some mammals) (see Image, left) or are attracted by the light and enter the lit area, leading to entrapment inside and possibly death (see Image, right). This can subsequently lead to habitat loss and segmentation, reduces available resources, increases competition and can change predation. All artificial light at night that exceeds the equivalent of that of naturally occurring moonlight lunar phase has negative effects on physiology, behavior, and life-history traits.