A manor house was historically the main residence of the lord of the manor. The house formed the administrative centre of a manor in the European feudal system; within its great hall were usually held the lord's manorial courts, communal meals with manorial tenants and great banquets. The term is today loosely (though erroneously) applied to various English country houses, mostly at the smaller end of the spectrum, sometimes dating from the Late Middle Ages, which currently or formerly house the landed gentry.

Manor houses were sometimes fortified, albeit not as fortified as castles, but this was often more for show than for defence. They existed in most European countries where feudalism was present.

The lord of the manor may have held several properties within a county or, for example in the case of a feudal baron, spread across a kingdom, which he occupied only on occasional visits. Even so, the business of the manor was directed and controlled by regular manorial courts, which appointed manorial officials such as the bailiff, granted copyhold leases to tenants, resolved disputes between manorial tenants and administered justice in general. A large and suitable building was required within the manor for such purpose, generally in the form of a great hall, and a solar might be attached to form accommodation for the lord.

The produce of a small manor might be insufficient to feed a lord and his large family for a full year, and thus he would spend only a few months at each manor and move on to another where stores had been laid up. This also gave the opportunity for the vacated manor house to be cleaned, especially important in the days of the cess-pit, and repaired. Thus such non-resident lords needed to appoint a steward or seneschal to act as their deputy in such matters and to preside at the manorial courts of his different manorial properties. The day-to-day administration was carried out by a resident official in authority at each manor, who in England was called a bailiff, or reeve.

Although not typically built with strong fortifications as were castles, many manor-houses were fortified, which required a royal licence to crenellate. They were often enclosed within walls or ditches which often also included agricultural buildings. Arranged for defence against roaming bands of robbers and thieves, in days long before police, they were often surrounded by a moat with a drawbridge, and were equipped with gatehouses and watchtowers, but not, as for castles, with a keep, large towers or lofty curtain walls designed to withstand a siege. The primary feature of the manor house was its great hall, to which subsidiary apartments were added as the lessening of feudal warfare permitted more peaceful domestic life.

By the beginning of the 16th century, manor houses as well as small castles began to acquire the character and amenities of the residences of country gentlemen, and many defensive elements were dispensed with, for example Sutton Place in Surrey, c. 1521. A late 16th-century transformation produced many of the smaller Renaissance châteaux of France and the numerous country mansions of the Elizabethan and Jacobean styles in England. These would eventually evolve into country houses with the estate replacing the manor.

Manor houses were often built in close proximity to the village for ease, as they served not just as a home for the lord of the manor, but as a centre of administration for those who lived or travelled within the bounds of the manor. In some instances, they needed to be able to hold meetings of the Manorial court.

Nearly every large medieval manor house had its own deer-park adjoining, imparked (i.e. enclosed) by royal licence, which served primarily as a store of food in the form of venison. Within these licensed parks deer could not be hunted by royalty (with its huge travelling entourage which needed to be fed and entertained), nor by neighbouring land-owners nor by any other persons.