Hadley Green is a 10 hectare Site of Metropolitan Importance for Nature Conservation in Monken Hadley in the London Borough of Barnet. It is an area of acid grassland interspersed with trees, and has several ponds. The acid grassland, ditches and ponds have several regionally rare species of plants, and the invertebrate fauna include eleven species of dragonflies and damselflies.
The reserve straddles the Great North Road between Hadley Green Road and Fold Lane. It is reputedly the site of a decisive battle in the Wars of the Roses, the Battle of Barnet in 1471. The land is a traditional village common and was grazed by villagers' animals for hundreds of years until the 20th century. It was secured for the people of Hadley parish as public open space in 1818.
- "iGiGL – helping you find London’s parks and wildlife sites". Greenspace Information for Greater London. 2006.
- "Hadley Green". Greenspace Information for Greater London. 2006. Retrieved 9 September 2012.
- Hadley Green Noticeboard
- Hadley Green, London Gardens Online