Lorraine is a historical area of Eastern France that today falls within the administrative region of Grand Est. It was the medieval kingdom called Lotharingia (855–959 AD), after Emperor Lothair I or King Lothair II, which extended further north and came to be ruled by the Holy Roman Empire as the Duchy of Lorraine, before the Kingdom of France annexed it in 1766.

From 1982 until January 2016, Lorraine was an administrative region of France. In 2016, under a reorganisation, it became part of the new region Grand Est. As a region in modern France, Lorraine consisted of the four departments Meurthe-et-Moselle, Meuse, Moselle and Vosges (from a historical point of view the Haute-Marne department is also located in the region), containing 2,337 communes. Metz is the regional prefecture. The largest metropolitan area of Lorraine is Nancy, which was the seat of the duchy for centuries.

To the north, Lorraine borders Germany, Belgium, and Luxembourg. In French, its male inhabitants are called Lorrains and its female inhabitants are called Lorraines. The population of Lorraine is about 2,356,000.

Lorraine's borders have changed often in its long history. The location of Lorraine led to it being a paramount strategic asset at the crossroads of four nations. This, along with its political alliances, marriage alliances, and the ability of rulers over the centuries to choose sides between East and West, gave it a powerful and important role in European history. Its rulers intermarried with royal families over all of Europe, played kingmaker, and seated rulers on the thrones of the Holy Roman Empire and the Austro-Hungarian Empire, and others.

In 840, Charlemagne's son Louis the Pious died. The Carolingian Empire was divided among Louis' three sons by the Treaty of Verdun of 843. The middle realm, known as Middle Francia, went to Lothair I, reaching from Frisia in Northern Germany through the Low Countries, Eastern France, Burgundy, Provence, Northern Italy, and down to Rome. On the death of Lothair I, Middle Francia was divided in three by the Treaty of Prüm in 855, with the northern third called Lotharingia and going to Lothair II. Due to Lotharingia being sandwiched between East and West Francia, the rulers identified as a duchy from 903 onward, enabling the duchy to ally and align itself nominally with either eastern or western Carolingian kingdoms in order to survive and maintain its independence. Thus, it was a duchy in name but operated as an independent kingdom.

In 870, Lorraine allied with East Francia while remaining an autonomous duchy. In 962, when Otto I, Holy Roman Emperor, restored the Empire (restauratio imperii), Lorraine was designated as the autonomous Duchy of Lorraine within the Holy Roman Empire. It maintained this status until 1766, after which it was annexed under succession law by the Kingdom of France, via derivative aristocratic house alliances.

The succession within these houses, in tandem with other historical events, would have later restored Lorraine's status as its own duchy, but a vacuum in leadership occurred. Its duke Francois Stephen de Lorraine took the throne of the Holy Roman Empire as Francis I, and his brother Prince Charles Alexander of Lorraine became governor of the Austrian Netherlands. For political reasons, he decided to hide those heirs who were not born by his first wife, Archduchess Maria Anna of Austria, who was deceased when he took office.

The vacuum in leadership, the French Revolution, and the political results and changes issuing from the many nationalistic wars that followed in the next 130 years, ultimately resulted in Lorraine becoming a permanent part of the modern Republic of France. Because of wars, it came under control of Germany several times as the border between the nations shifted. While Lorrainian separatists do exist in the 21st century, their political power and influence is negligible. Lorraine separatism today consists more of preserving its cultural identity rather than seeking genuine political independence.