Nature-deficit disorder is a proposed set of behavioral problems that result when humans, especially children, spend less time outdoors. This putative condition is not recognized in standard medical manuals for mental disorders, such as the ICD-10 or the DSM-5.

This term was coined by Richard Louv in 2005. Louv claimed that the word "disorder" did not imply a medical condition but was rather a metaphor to describe the health costs of alienation from nature. He cited parental fears and a lack of access to natural landscapes as causes for the condition.

In the USA, the Children & Nature Network was co-founded by Louv to support people and organizations that work to reconnect children with nature. The unrelated No Child Left Inside movement has a similar mission and a presence in some US states.

In Colombia, OpEPA (Organización para la Educación y Protección Ambiental), founded in 1998, works to reconnect children and youth to nature so they can act with environmental responsibility.

Nature-deficit disorder is unrecognized by most medical institutions. Some preliminary research shows that lack of time outdoors does have negative effects on children's mental well-being.

Research on the impact of natural environments, particularly the concept of urban green space, has shown certain supporting claims:

Richard Louv has proposed certain causes for the putative condition of nature deficit disorder:

Research in the USA found that redlining has tended to limit the access of low-income and marginalized communities to green space. One study suggested additional exposure of these groups to the proposed nature-deficit disorder.