A green belt or greenbelt is a policy and land use designation used in land use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighbouring urban areas. Similar concepts are greenways or green wedges which have a linear character and may run through an urban area instead of around it. In essence, a green belt is an invisible line encircling a certain area, preventing development of the area allowing wildlife to return and be established.

In those countries which have them, the stated objectives of green belt policy are to:

The green belt has many benefits for people:

The effectiveness of green belts differs depending on location and country. They can often be eroded by urban rural fringe uses and sometimes, development 'jumps' over the green belt area, resulting in the creation of "satellite towns" which, although separated from the city by green belt, function more like suburbs than independent communities.

The Old Testament outlines a proposal for a green belt around the Levite towns in the Land of Israel Moses Maimonides expounded that the greenbelt plan from the Old Testament referred to all towns in ancient Israel. In the 7th century, Muhammad established a green belt around Medina. He did this by prohibiting any further removal of trees in a 12-mile long strip around the city. In 1580 Elizabeth I of England banned new building in a 3-mile wide belt around the City of London in an attempt to stop the spread of plague. However, it was possible to buy dispensations which reduced the effectiveness of the proclamation.

Wangari Muta Maathai (1 April 1940 – 25 September 2011) was a Kenyan environmental and political activist. She was educated in the United States at Mount St. Scholastica and the University of Pittsburgh, as well as the University of Nairobi in Kenya. In the 1970s, Maathai founded the Green Belt Movement, an environmental non-governmental organization focused on the planting of trees, environmental conservation, and women's rights. In 1986, she was awarded the Right Livelihood Award, and in 2004, she became the first African woman to receive the Nobel Peace Prize for "her contribution to sustainable development, democracy and peace." Maathai was an elected member of Parliament and served as assistant minister for Environment and Natural Resources in the government of President Mwai Kibaki between January 2003 and November 2005. Furthermore she was an Honorary Councillor of the World Future Council. In 2011, Maathai died of complications from ovarian cancer.

On 1 April 1940, Maathai was born in the village of Ihithe, Nyeri District, in the central highlands of the colony of Kenya. Her family was Kikuyu, the most populous ethnic group in Kenya, and had lived in the area for several generations. Around 1943, Maathai's family relocated to a white-owned farm in the Rift Valley, near the town of Nakuru, where her father had found work. Late in 1947, she returned to Ihithe with her mother, as two of her brothers were attending primary school in the village, and there was no schooling available on the farm where her father worked. Her father remained at the farm. Shortly afterward, at the age of eight, she joined her brothers at Ihithe Primary School.