Urban reforestation is the practice of planting trees, typically on a large scale, in urban environments. It may also include urban horticulture and urban farming.

Reasons for practicing urban reforestation include urban beautification; increasing shade; modifying the urban climate; improving air quality, such as by sequestering carbon dioxide; and restoration of urban forests after a natural disaster. Increased shade from urban reforestation can also lead to decreased energy costs, as heat from the sun is blocked from heating structures that use air conditioning. These benefits may aid in increasing local property values, filtering rainwater pollutants from the streets and thus improving water quality, and creating more habitats for wildlife, particularly endangered species.

Urban reforestation may also be effective because it does not require the purchase of a large piece of land to execute.

The Urban Reforestation organization in Australia is a grassroots organization that focuses on sustainable living in urban places.

The widespread reforestation in urban sites of Paris was launched in 2020 in order to reduce air pollution in the city. Anne Hidalgo, Mayor of Paris, stated that by the summer of 2023 63,500 trees were already planted, and by end of her term 170,000 will be planted in all.

Istanbul Metropolitan Municipality began a green project that covers 78,500 m² in Zeytinburnu to afforest the barren part of Zeytinburnu coast, and also the urban reforestation project provided continuity of the coast line Yedikule to Bakırköy for pedestrians.

Large scale urban reforestation programs in the United States include New York City's Million Tree Initiative and TreePeople in Los Angeles, which planted 1 million trees in preparation for the 1984 Summer Olympics and continued planting thereafter. In 2022, Boston announced a new forestry division to grow the tree canopy within the city.

Grassroots efforts include Friends of the Urban Forest in San Francisco, which advocates for the planting of street trees.