Knight is the English term for a social position originating in the Middle Ages. In the Commonwealth of Nations, knighthood is a non-heritable form of gentry. Elsewhere, the Spanish Caballero (related to "chivalry"), the Italian Cavaliere, the German Ritter (related to the English word "Rider" and the Swedish word Riddare), or the Polish Kawaler (for Modern Era knighthoods or Rycerz for medieval knighthoods) are commonly used in Continental Europe. Outside the British Commonwealth, the title is respected but may carry less significance, and thus may or may not appear, for example, in the mass media and other publications. There are technically differing levels of knighthood (see Order of the British Empire), but in practice these are even more symbolic than the title itself today and thus only express the greatness of the recipient's achievements in the eyes of the Crown.

The British legend of King Arthur, popularised throughout Europe in the Middle Ages by Geoffrey of Monmouth in his Historia Regum Britanniae ("History of the Kings of Britain") written in the 1130s, and Sir Thomas Malory's Le Morte d'Arthur (The Death of Arthur) written in 1485, were important in defining the ideal of chivalry which is essential to the European ideal of the knight as an elite warrior sworn to uphold the values of faith, loyalty, courage and honour such as Knights Templar. Also the (Spanish) legend Rodrigo Diaz de Vivar known as El Cid who was a famous Spanish knight who fought to bring Christianity back to Spain. In a parallel development in Japan, Bushidō ("Way of the Warrior") written down between the 9th and 12th centuries and Heike monogatari ("Tale of the Heike") popularised by Kakuichi in 1371, defined the ideal of the Samurai warrior.

The Middle Ages form the middle period in a traditional schematic division of European history into three "ages": the classical civilization of Antiquity, the Middle Ages and Modern Times. The idea of such a periodisation is attributed to Flavio Biondo, an Italian Renaissance humanist historian.

The Middle Ages are commonly dated from the fall of the Western Roman Empire (or by some scholars, before that) in the 5th century to the beginning of the Early Modern Period in the 16th century, marked by the rise of nation-states, the division of Western Christianity in the Reformation, the rise of humanism in the Italian Renaissance, and the beginnings of European overseas expansion which allowed for the Columbian Exchange. There is some variation in the dating of the edges of these periods which is due mainly to differences in specialization and focus of individual scholars. Commonly seen periodisation ranges span the years ca. 400–476 AD (the sackings of Rome by the Visigoths to the deposing of Romulus Augustus) to ca. 1453–1517 (the Fall of Constantinople to the Protestant Reformation begun with Martin Luther's Ninety-Five Theses). Dates are approximate, and are based upon nuanced arguments; for other dating schemes and the reasoning behind them, see "periodisation issues", below.

The Middle Ages witnessed the first sustained urbanization of northern and western Europe. Many modern European states owe their origins to events unfolding in the Middle Ages; present European political boundaries are, in many regards, the result of the military and dynastic achievements during this tumultuous period.