A royal forest, occasionally known as a kingswood (Latin: silva regis), is an area of land with different definitions in England, Wales, Scotland and Ireland. The term forest in the ordinary modern understanding refers to an area of wooded land; however, the original medieval sense was closer to the modern idea of a "preserve" – i.e. land legally set aside for specific purposes such as royal hunting – with less emphasis on its composition. There are also differing and contextual interpretations in Continental Europe derived from the Carolingian and Merovingian legal systems.

In Anglo-Saxon England, though the kings were great huntsmen, they never set aside areas declared to be "outside" (Latin foris) the law of the land. Historians find no evidence of the Anglo-Saxon monarchs (c. 500 to 1066) creating forests. However, under the Norman kings (after 1066), by royal prerogative forest law was widely applied. The law was designed to protect the venison and the vert, the "noble" animals of the chase – notably red and fallow deer, the roe deer, and the wild boar – and the greenery that sustained them. Forests were designed as hunting areas reserved for the monarch or (by invitation) the aristocracy. The concept was introduced by the Normans to England in the 11th century, and at the height of this practice in the late 12th and early 13th centuries, fully one-third of the land area of Southern England was designated as royal forest. At one stage in the 12th century, all of Essex was afforested. On his accession Henry II declared all of Huntingdonshire to be a royal forest.

Afforestation, in particular the creation of the New Forest, figured large in the folk history of the "Norman yoke", which magnified what was already a grave social ill: "the picture of prosperous settlements disrupted, houses burned, peasants evicted, all to serve the pleasure of the foreign tyrant, is a familiar element in the English national story .... The extent and intensity of hardship and of depopulation have been exaggerated", H. R. Loyn observed. Forest law prescribed harsh punishment for anyone who committed any of a range of offences within the forests; by the mid-17th century, enforcement of this law had died out, but many of England's woodlands still bore the title "Royal Forest". During the Middle Ages, the practice of reserving areas of land for the sole use of the aristocracy was common throughout Europe.

Royal forests usually included large areas of heath, grassland and wetland – anywhere that supported deer and other game. In addition, when an area was initially designated forest, any villages, towns and fields that lay within it were also subject to forest law. This could foster resentment as the local inhabitants were then restricted in the use of land they had previously relied upon for their livelihoods; however, common rights were not extinguished, but merely curtailed.