England in the Middle Ages concerns the history of England during the medieval period, from the end of the 5th century through to the start of the early modern period in 1485. When England emerged from the collapse of the Roman Empire, the economy was in tatters and many of the towns abandoned. After several centuries of Germanic immigration, new identities and cultures began to emerge, developing into kingdoms that competed for power. A rich artistic culture flourished under the Anglo-Saxons, producing epic poems such as Beowulf and sophisticated metalwork. The Anglo-Saxons converted to Christianity in the 7th century, and a network of monasteries and convents were built across England. In the 8th and 9th centuries, England faced fierce Viking attacks, and the fighting lasted for many decades. Eventually, Wessex was established as the most powerful kingdom and promoted the growth of an English identity. Despite repeated crises of succession and a Danish seizure of power at the start of the 11th century, it can also be argued that by the 1060s England was a powerful, centralised state with a strong military and successful economy.

The Norman invasion of England in 1066 led to the defeat and replacement of the Anglo-Saxon elite with Norman and French nobles and their supporters. William the Conqueror and his successors took over the existing state system, repressing local revolts and controlling the population through a network of castles. The new rulers introduced a feudal approach to governing England, eradicating the practice of slavery, but creating a much wider body of unfree labourers called serfs. The position of women in society changed as laws regarding land and lordship shifted. England's population more than doubled during the 12th and 13th centuries, fueling an expansion of the towns, cities, and trade, helped by warmer temperatures across Northern Europe. A new wave of monasteries and friaries was established while ecclesiastical reforms led to tensions between successive kings and archbishops. Despite developments in England's governance and legal system, infighting between the Anglo-Norman elite resulted in multiple civil wars and the loss of Normandy.

The 14th century in England saw the Great Famine and the Black Death, catastrophic events that killed around half of England's population, throwing the economy into chaos, and undermining the old political order. Social unrest followed, resulting in the Peasants' Revolt of 1381, while the changes in the economy resulted in the emergence of a new class of gentry, and the nobility began to exercise power through a system termed bastard feudalism. Nearly 1,500 villages were deserted by their inhabitants and many men and women sought new opportunities in the towns and cities. New technologies were introduced, and England produced some of the great medieval philosophers and natural scientists. English kings in the 14th and 15th centuries laid claim to the French throne, resulting in the Hundred Years' War. At times, England enjoyed huge military success, with the economy buoyed by profits from the international wool and cloth trade. However, by 1450, England was in crisis; the country was facing military failure in France as well as an ongoing recession. More social unrest broke out, followed by the Wars of the Roses, fought between rival factions of the English nobility. Henry VII's victory in 1485 over Richard III at the Battle of Bosworth Field conventionally marks the end of the Middle Ages in England and the start of the Early Modern period.

At the start of the Middle Ages, England was a part of Britannia, a former province of the Roman Empire. The local economy had once been dominated by imperial Roman spending on a large military establishment, which in turn helped to support a complex network of towns, roads, and villas. At the end of the 4th century, however, Roman forces had been largely withdrawn, and this economy collapsed. Germanic settlers began to arrive in increasing numbers during the 5th and 6th centuries, establishing small farms and settlements, and their language, Old English, swiftly spread as more settlers arrived and those of the previous inhabitants who had not moved west or to Brittany switched from Common Brittonic and British Latin to the migrants' language. New political and social identities emerged, including an Anglian culture in the east of England and a Saxon culture in the south, with local groups establishing regiones, small polities ruled over by powerful families and individuals. By the 7th century, some rulers, including those of Wessex, East Anglia, Essex, and Kent, had begun to term themselves kings, living in villae regales, royal centres, and collecting tribute from the surrounding regiones; these kingdoms are often referred to as the Heptarchy.

In the 7th century, the Kingdom of Mercia rose to prominence under the leadership of King Penda. Mercia invaded neighbouring lands until it loosely controlled around 50 regiones covering much of England. Mercia and the remaining kingdoms, led by their warrior elites, continued to compete for territory throughout the 8th century. Massive earthworks, such as the defensive dyke built by Offa of Mercia, helped to defend key frontiers and towns. In 789, however, the first Scandinavian raids on England began; these Viking attacks grew in number and scale until in 865 the Danish micel here or Great Army, invaded England, captured York and defeated the kingdom of East Anglia. Mercia and Northumbria fell in 875 and 876, and Alfred of Wessex was driven into internal exile in 878.

However, in the same year Alfred won a decisive victory against the Danes at the Battle of Edington, and he exploited the fear of the Viking threat to raise large numbers of men and using a network of defended towns called burhs to defend his territory and mobilise royal resources. Suppressing internal opposition to his rule, Alfred contained the invaders within a region known as the Danelaw. Under his son, Edward the Elder, and his grandson, Æthelstan, Wessex expanded further north into Mercia and the Danelaw, and by the 950s and the reigns of Eadred and Edgar, York was finally permanently retaken from the Vikings. The West Saxon rulers were now kings of the Angelcynn, that is of the whole English folk.

With the death of Edgar, however, the royal succession became problematic. Æthelred took power in 978 following the murder of his brother Edward, but England was then invaded by Sweyn Forkbeard, the son of a Danish king. Attempts to bribe Sweyn not to attack using danegeld payments failed, and he took the throne in 1013. Swein's son, Cnut, liquidated many of the older English families following his seizure of power in 1016. Æthelred's son, Edward the Confessor, had survived in exile in Normandy and returned to claim the throne in 1042. Edward was childless, and the succession again became a concern. England became dominated by the Godwin family, who had taken advantage of the Danish killings to acquire huge wealth. When Edward died in 1066, Harold Godwinson claimed the throne, defeating his rival Norwegian claimant, Harald Hardrada, at the battle of Stamford Bridge.

In 1066, William, Duke of Normandy, took advantage of the English succession crisis to begin the Norman Conquest. With an army of Norman followers and mercenaries, he defeated Harold at the Battle of Hastings on 14 October 1066 and rapidly occupied the south of England. William used a network of castles to control the major centres of power, granting extensive lands to his main Norman followers and co-opting or eliminating the former Anglo-Saxon elite. Major revolts followed, which William suppressed before intervening in the north-east of England, establishing Norman control of York and devastating the region. Some Norman lords used England as a launching point for attacks into South and North Wales, spreading up the valleys to create new Marcher territories. By the time of William's death in 1087, England formed the largest part of an Anglo-Norman empire, ruled over by a network of nobles with landholdings across England, Normandy, and Wales. England's growing wealth was critical in allowing the Norman kings to project power across the region, including funding campaigns along the frontiers of Normandy.