Louis the Pious (also known as Louis I, Louis the Fair, and Louis the Debonaire, Dutch: Lodewijk de Vrome, German: Ludwig der Fromme, French: Louis le Pieux or Louis le Débonnaire, Italian: Luigi il Pio or Ludovico il Pio, Spanish: Luis el Piadoso or Ludovico Pío) was Emperor and King of the Franks from 814 to his death in 840.

Rule in Aquitaine

Louis was born at the Carolingian villa of Cassinogilum, according to Eginhard and the anonymous chronicler called Astronomus, the third son of Charlemagne by his third wife, Hildegard, while his father Charlemagne led a military campaign in Spain. Though Cassinogilum was to be one of his habitual residences in the Kingdom of Aquitaine for years, the location of his birthplace has been disputed. Louis was crowned king of Aquitaine as a child in 781 and sent there with regents and a court to rule in order to quiet rebellions which were forming after Charlemagne's defeat by the Moors in Spain (778). In 794, Charlemagne settled four former Gallo-Roman villas on Louis, in the thought that he would reside in the winters in each in turn: Doué-la-Fontaine in today's Anjou, Ebreuil in Allier, Angeac-Charente, and the disputed Cassinogilum. Charlemagne's intention was to see all his sons brought up as natives of their given territories, wearing the national costume of the region and ruling by the local customs. Thus were the children sent to their respective realms at so young an age. Each kingdom had its importance in keeping some frontier, Louis's was the Spanish March. In 797, Barcelona, the greatest city of the Marca, fell to the Franks when Zeid, its governor, rebelled against Córdoba and, failing, handed it to them. The Umayyad authority recaptured it in 799. However, Louis marched the entire army of his kingdom, including Gascons with their duke Sancho I, Provençals under Leibulf, and Goths under Bera, over the Pyrenees and besieged it for two years, wintering there from 800 to 801, when it capitulated. The sons were not given independence from central authority, however, and Charlemagne ingrained in them the concepts of empire and unity by sending them on military expeditions far from their home bases. Louis campaigned in the Mezzogiorno against the Beneventans at least once.

Louis was one of Charlemagne's four legitimate sons, but the eldest, Pepin the Hunchback, had consented to a rebellion against his father and was banished to a monastery. That left three in active life and, like most Frankish men, Louis had expected to share his inheritance with his brothers, Charles the Younger, King of Neustria, and Pepin, King of Italy. In the Divisio Regnorum of 806, Charlemagne had slated Charles the Younger as his successor as emperor and chief king, ruling over the Frankish heartland of Neustria and Austrasia, while giving Pepin the Iron Crown of Lombardy, which Charlemagne possessed by conquest. To Louis's kingdom of Aquitaine, he added Septimania, Provence, and part of Burgundy.

But in the event, Charlemagne's other legitimate sons died — Pepin in 810 and Charles in 811 and Louis alone remained to be crowned co-emperor with Charlemagne in 813. On his father's death in 814, he inherited the entire Frankish kingdom and all its possessions (with the sole exception of Italy, which remained within Louis' empire, but under the direct rule of Bernard, Pepin's son).

Emperor

He was in his villa of Doué-la-Fontaine, Anjou, when he received news of his father's passing. Hurrying to Aachen, he crowned himself and was proclaimed by the nobles with shouts of Vivat Imperator Ludovicus.

As a motto of his reign, he minted the reverse of his coins with the legend Renovatio Regni Francorum. In this, he intended to signify the renewal of the empire to a lost moral grandeur. He quickly enacted a "moral purge", in which he sent all of his unmarried sisters to nunneries, forgoing their diplomatic use as hostage brides in favour of the security of avoiding the entanglements that powerful brothers-in-law might bring. He spared his illegitimate half-brothers and tonsured his father's cousins, Adalard and Wala, shutting them up in Noirmoutier and Corbie, respectively, despite the latter's initial loyalty.