Kielder Forest is a large forestry plantation in Northumberland, England, surrounding Kielder village and the Kielder Water reservoir. It is the largest man-made woodland in England with three-quarters of its 250 square miles covered by forest. The majority of the forest lies within Kielder Water and Forest Park, with the southern tip known as Wark Forest lying within Northumberland National Park. The forest is next to the Anglo-Scottish border.