Charlemagne (Latin: Carolus Magnus or Karolus Magnus, meaning Charles the Great; 2 April 742 – 28 January 814) was King of the Franks from 768 to his death. He expanded the Frankish kingdom into a Frankish Empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned Imperator Augustus by Pope Leo III on 25 December 800 which temporarily made him a rival of the Byzantine Emperor in Constantinople. His rule is also associated with the Carolingian Renaissance, a revival of art, religion, and culture through the medium of the Catholic Church. Through his foreign conquests and internal reforms, Charlemagne helped define both Western Europe and the Middle Ages. He is numbered as Charles I in the regnal lists of France, Germany (where he is known as Karl der Große), and the Holy Roman Empire.

The son of King Pippin the Short and Bertrada of Laon, he succeeded his father and co-ruled with his brother Carloman I. The latter got on badly with Charlemagne, but war was prevented by the sudden death of Carloman in 771. Charlemagne continued the policy of his father towards the papacy and became its protector, removing the Lombards from power in Italy, and waging war on the Saracens, who menaced his realm from Spain. It was during one of these campaigns that Charlemagne experienced the worst defeat of his life, at the Battle of Roncesvalles (778) memorialised in the Song of Roland. He also campaigned against the peoples to his east, especially the Saxons, and after a protracted war subjected them to his rule. By forcibly converting them to Christianity, he integrated them into his realm and thus paved the way for the later Ottonian dynasty.

Today he is regarded not only as the founding father of both French and German monarchies, but also as the father of Europe: his empire united most of Western Europe for the first time since the Romans, and the Carolingian renaissance encouraged the formation of a common European identity.

By the 6th century, the Franks were Christianised, and Francia ruled by the Merovingians had become the most powerful of the kingdoms which succeeded the Western Roman Empire. But following the Battle of Tertry, the Merovingians declined into a state of powerlessness, for which they have been dubbed do-nothing kings (rois fainéants). Almost all government powers of any consequence were exercised by their chief officer, the mayor of the palace or major domus.

In 687, Pippin of Herstal, mayor of the palace of Austrasia, ended the strife between various kings and their mayors with his victory at Tertry and became the sole governor of the entire Frankish kingdom. Pippin himself was the grandson of two most important figures of the Austrasian Kingdom, Saint Arnulf of Metz and Pippin of Landen. Pippin the Middle was eventually succeeded by his illegitimate son Charles, later known as Charles Martel (the Hammer). After 737, Charles governed the Franks without a king on the throne but desisted from calling himself "king." Charles was succeeded by his sons Carloman and Pippin the Short, the father of Charlemagne. To curb separatism in the periphery of the realm, the brothers placed on the throne Childeric III, who was to be the last Merovingian king.

After Carloman resigned his office, Pippin had Childeric III deposed with Pope Zachary's approval. In 751, Pippin was elected and anointed King of the Franks and in 754, Pope Stephen II again anointed him and his young sons, now heirs to the great realm which already covered most of western and central Europe. Thus was the Merovingian dynasty replaced by the Carolingian dynasty, named after Pippin's father Charles Martel.

Under the new dynasty, the Frankish kingdom spread to encompass an area including most of Western Europe. The division of that kingdom formed France and Germany; and the religious, political, and artistic evolutions originating from a centrally-positioned Francia made a defining imprint on the whole of Western Europe.

Charlemagne is believed to have been born in 742 in Herstal (where his father was born, a town close to Liège in modern day Belgium), the region from where both the Merovingian and Carolingian families originate. He went to live in his father's villa in Jupille when he was around seven. Charlemagne's native language is a matter of controversy. It was probably a Germanic dialect of the Ripuarian Franks, but linguists differ on its identity and chronology. Apart from his native language he also spoke Latin "as fluently as his own tongue" and understood a bit of Greek. Though no description from Charlemagne's lifetime exists, his personal appearance is known from a good description by Einhard, author of the biography Vita Karoli Magni.

He was heavily built, sturdy, and of considerable stature, although not exceptionally so, since his height was seven times the length of his own foot. He had a round head, large and lively eyes, a slightly larger nose than usual, white but still attractive hair, a bright and cheerful expression, a short and fat neck, and a slightly protruding stomach. His voice was clear, but a little higher than one would have expected for a man of his build. He enjoyed good health, except for the fevers that affected him in the last few years of his life. Toward the end he dragged one leg. Even then, he stubbornly did what he wanted and refused to listen to doctors, indeed he detested them, because they wanted to persuade him to stop eating roast meat, as was his wont, and to be content with boiled meat.

Charlemagne wore the traditional, inconspicuous and distinctly non-aristocratic costume of the Frankish people. He wore a blue cloak and always carried a sword with him. The typical sword was of a golden or silver hilt. He wore fancy jewelled swords to banquets or ambassadorial receptions. He could rise to the occasion when necessary. On great feast days, he wore embroidery and jewels on his clothing and shoes. He had a golden buckle for his cloak on such occasions and would appear with his great diadem, but he despised such apparel and usually dressed like the common people.

Charlemagne was the eldest child of Pippin the Short (714 – 24 September 768, reigned from 751) and his wife Bertrada of Laon (720 – 12 July 783), daughter of Caribert of Laon and Bertrada of Cologne. Records name only Carloman, Gisela, and a short-lived child named Pippin as his younger siblings. On the death of Pippin, the kingdom of the Franks was divided—following tradition—between Charlemagne and Carloman. Charles took the outer parts of the kingdom, bordering on the sea, namely Neustria, western Aquitaine, and the northern parts of Austrasia, while Carloman retained the inner parts: southern Austrasia, Septimania, eastern Aquitaine, Burgundy, Provence, and Swabia, lands bordering on Italy. On 9 October, immediately after the funeral of their father, both the kings withdrew from Saint Denis to be proclaimed by their nobles and consecrated by the bishops, Charlemagne in Noyon and Carloman in Soissons.

The first event of the brothers' reign was the rising of the Aquitainians and Gascons, in 769, in that territory split between the two kings. Years before Pippin had suppressed the revolt of Waifer, Duke of Aquitaine. Now, one Hunald led the Aquitainians as far north as Angoulême. Charlemagne met Carloman, but Carloman refused to participate and returned to Burgundy. Charlemagne went to war, leading an army to Bordeaux, where he set up a camp at Fronsac. Hunold was forced to flee to the court of Duke Lupus II of Gascony. Lupus, fearing Charlemagne, turned Hunold over in exchange for peace. He was put in a monastery. Aquitaine was finally fully subdued by the Franks.

The brothers maintained lukewarm relations with the assistance of their mother Bertrada, but in 770 Charlemagne signed a treaty with Duke Tassilo III of Bavaria and married a Lombard Princess (commonly known today as Desiderata), the daughter of King Desiderius, to surround Carloman with his own allies. Though Pope Stephen III first opposed the marriage with the Lombard princess, he would soon have little to fear from a Frankish-Lombard alliance. Less than a year after his marriage, Charlemagne repudiated Desiderata, and quickly remarried to a 13-year-old Swabian named Hildegard. The repudiated Desiderata returned to her father's court at Pavia. The Lombard's wrath was now aroused and he would gladly have allied with Carloman to defeat Charles. But before war could break out, Carloman died on 5 December 771. Carloman's wife Gerberga fled to Desiderius' court with her sons for protection.

At the succession of Pope Hadrian I in 772, he demanded the return of certain cities in the former exarchate of Ravenna as in accordance with a promise of Desiderius' succession. Desiderius instead took over certain papal cities and invaded the Pentapolis, heading for Rome. Hadrian sent embassies to Charlemagne in autumn requesting he enforce the policies of his father, Pippin. Desiderius sent his own embassies denying the pope's charges. The embassies both met at Thionville and Charlemagne upheld the pope's side. Charlemagne promptly demanded what the pope had demanded and Desiderius promptly swore never to comply. Charlemagne and his uncle Bernard crossed the Alps in 773 and chased the Lombards back to Pavia, which they then besieged. Charlemagne temporarily left the siege to deal with Adelchis, son of Desiderius, who was raising an army at Verona. The young prince was chased to the Adriatic littoral and he fled to Constantinople to plead for assistance from Constantine V, who was waging war with Bulgaria. The siege lasted until the spring of 774, when Charlemagne visited the pope in Rome. There he confirmed his father's grants of land, with some later chronicles claiming—falsely—that he also expanded them, granting Tuscany, Emilia, Venice, and Corsica. The pope granted him the title patrician. He then returned to Pavia, where the Lombards were on the verge of surrendering. In return for their lives, the Lombards surrendered and opened the gates in early summer. Desiderius was sent to the abbey of Corbie and his son Adelchis died in Constantinople a patrician. Charles, unusually, had himself crowned with the Iron Crown and made the magnates of Lombardy do homage to him at Pavia. Only Duke Arechis II of Benevento refused to submit and proclaimed independence. Charlemagne was now master of Italy as king of the Lombards. He left Italy with a garrison in Pavia and few Frankish counts in place that very year.

There was still instability, however, in Italy. In 776, Dukes Hrodgaud of Friuli and Hildeprand of Spoleto rebelled. Charlemagne rushed back from Saxony and defeated the duke of Friuli in battle. The duke was slain. The duke of Spoleto signed a treaty. Their co-conspirator, Arechis, was not subdued and Adelchis, their candidate in Byzantium, never left that city. Northern Italy was now faithfully his. In 787 Charlemagne directed his attention towards Benevento, where Arechis was reigning independently. He besieged Salerno and Arechis submitted to vassalage. However, with his death in 792, Benevento again proclaimed independence under his son Grimoald III. Grimoald was attacked by armies of Charles or his sons many times, but Charlemagne himself never returned to the Mezzogiorno and Grimoald never was forced to surrender to Frankish suzerainty.

During the first peace of any substantial length (780–782), Charles began to appoint his sons to positions of authority within the realm, in the tradition of the kings and mayors of the past. In 781 he made his two younger sons kings, having them crowned by the Pope. The elder of these two, Carloman, was made king of Italy, taking the Iron Crown which his father had first worn in 774, and in the same ceremony was renamed "Pippin." The younger of the two, Louis, became king of Aquitaine. Charlemagne ordered Pippin and Louis to be raised in the customs of their kingdoms, and he gave their regents some control of their subkingdoms, but real power was always in his hands, though he intended each to inherit their realm some day. Nor did he tolerate insubordination in his sons: in 792, he banished his eldest, though illegitimate, son, Pippin the Hunchback, to the monastery of Prüm, because the young man had joined a rebellion against him. Charles was determined to have his children educated, including his daughters, as he himself was not. His children were taught all the arts and his daughters were learned in the way of women. His sons took archery, horsemanship, and other outdoors activities.

The sons fought many wars on behalf of their father when they came of age. Charles was mostly preoccupied with the Bretons, whose border he shared and who insurrected on at least two occasions and were easily put down, but he was also sent against the Saxons on multiple occasions. In 805 and 806, he was sent into the Böhmerwald (modern Bohemia) to deal with the Slavs living there (Czechs). He subjected them to Frankish authority and devastated the valley of the Elbe, forcing a tribute on them. Pippin had to hold the Avar and Beneventan borders, but also fought the Slavs to his north. He was uniquely poised to fight the Byzantine Empire when finally that conflict arose after Charlemagne's imperial coronation and a Venetian rebellion. Finally, Louis was in charge of the Spanish March and also went to southern Italy to fight the duke of Benevento on at least one occasion. He took Barcelona in a great siege in the year 797.

According to the Muslim historian Ibn al-Athir, the Diet of Paderborn had received the representatives of the Muslim rulers of Zaragoza, Girona, Barcelona, and Huesca. Their masters had been cornered in the Iberian peninsula by Abd ar-Rahman I, the  mayyad emir of Córdoba. These Moorish or "Saracen" rulers offered their homage to the great king of the Franks in return for military support. Seeing an opportunity to extend Christendom and his own power and believing the Saxons to be a fully conquered nation, he agreed to go to Spain. In 778, he led the Neustrian army across the Western Pyrenees, while the Austrasians, Lombards, and Burgundians passed over the Eastern Pyrenees. The armies met at Zaragoza and Charlemagne received the homage of the Muslim rulers, Sulayman al-Arabi and Kasmin ibn Yusuf, but the city did not fall for him. Indeed, Charlemagne was facing the toughest battle of his career where the Muslims had the upper hand and forced him to retreat. He decided to go home, since he could not trust the Basques, whom he had subdued by conquering Pamplona. He turned to leave Iberia, but as he was passing through the Pass of Roncesvalles one of the most famous events of his long reign occurred. The Basques fell on his rearguard and baggage train, utterly destroying it. The Battle of Roncevaux Pass, less a battle than a mere skirmish, left many famous dead: among which were the seneschal Eggihard, the count of the palace Anselm, and the warden of the Breton March, Roland, inspiring the subsequent creation of the Song of Roland (La Chanson de Roland).

The conquest of Italy brought Charlemagne in contact with the Saracens who, at the time, controlled the Mediterranean. Pippin, his son, was much occupied with Saracens in Italy. Charlemagne conquered Corsica and Sardinia at an unknown date and in 799 the Balearic Islands. The islands were often attacked by Saracen pirates, but the counts of Genoa and Tuscany (Boniface) kept them at bay with large fleets until the end of Charlemagne's reign. Charlemagne even had contact with the caliphal court in Baghdad. In 797 (or possibly 801), the caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian elephant named Abul-Abbas and a clock.

In Hispania the struggle against the Moors continued unabated throughout the latter half of his reign. His son Louis was in charge of the Spanish border. In 785, his men captured Gerona permanently and extended Frankish control into the Catalan littoral for the duration of Charlemagne's reign (and much longer, it remained nominally Frankish until the Treaty of Corbeil in 1258). The Muslim chiefs in the northeast of Islamic Spain were constantly revolting against Córdoban authority and they often turned to the Franks for help. The Frankish border was slowly extended until 795, when Gerona, Cardona, Ausona, and Urgel were united into the new Spanish March, within the old duchy of Septimania. In 797 Barcelona, the greatest city of the region, 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 of Aquitaine marched the entire army of his kingdom over the Pyrenees and besieged it for two years, wintering there from 800 to 801, when it capitulated. The Franks continued to press forwards against the emir. They took Tarragona in 809 and Tortosa in 811. The last conquest brought them to the mouth of the Ebro and gave them raiding access to Valencia, prompting the Emir al-Hakam I to recognise their conquests in 812.

Charlemagne was engaged in almost constant battle throughout his reign, often at the head of his elite scara bodyguard squadrons, with his legendary sword Joyeuse in hand. After thirty years of war and eighteen battles—the Saxon Wars—he conquered Saxonia and proceeded to convert the conquered to Roman Catholicism, sometimes using force. The Saxons were divided into four subgroups in four regions. Nearest to Austrasia was Westphalia and furthest away was Eastphalia. In between these two kingdoms was that of Engria and north of these three, at the base of the Jutland peninsula, was Nordalbingia. In his first campaign, Charlemagne forced the Engrians in 773 to submit and cut down an Irminsul pillar near Paderborn. The campaign was cut short by his first expedition to Italy. He returned in the year 775, marching through Westphalia and conquering the Saxon fort of Sigiburg. He then crossed Engria, where he defeated the Saxons again. Finally, in Eastphalia, he defeated a Saxon force, and its leader Hessi converted to Christianity. He returned through Westphalia, leaving encampments at Sigiburg and Eresburg, which had, up until then, been important Saxon bastions. All Saxony but Nordalbingia was under his control, but Saxon resistance had not ended. Following his campaign in Italy subjugating the dukes of Friuli and Spoleto, Charlemagne returned very rapidly to Saxony in 776, where a rebellion had destroyed his fortress at Eresburg. The Saxons were once again brought to heel, but their main leader, duke Widukind, managed to escape to Denmark, home of his wife. Charlemagne built a new camp at Karlstadt. In 777, he called a national diet at Paderborn to integrate Saxony fully into the Frankish kingdom. Many Saxons were baptised. In the summer of 779, he again invaded Saxony and reconquered Eastphalia, Engria, and Westphalia. At a diet near Lippe, he divided the land into missionary districts and himself assisted in several mass baptisms (780). He then returned to Italy and, for the first time, there was no immediate Saxon revolt. In 780 Charlemagne decreed the death penalty for all Saxons who failed to be baptised, who failed to keep Christian festivals, and who cremated their dead. Saxony had peace from 780 to 782. He returned in 782 to Saxony and instituted a code of law and appointed counts, both Saxon and Frank. The laws were draconian on religious issues, and the indigenous forms of Germanic polytheism were gravely threatened by Christianisation. This stirred a renewal of the old conflict. That year, in autumn, Widukind returned and led a new revolt, which resulted in several assaults on the church. In response, at Verden in Lower Saxony, Charlemagne allegedly ordered the beheading of 4,500 Saxons who had been caught practising their native paganism after conversion to Christianity, known as the Massacre of Verden ("Verdener Blutgericht"). The massacre triggered three years of renewed bloody warfare (783-785). During this war the Frisians were also finally subdued and a large part of their fleet was burned. The war ended with Widukind accepting baptism. Thereafter, the Saxons maintained the peace for seven years, but in 792 the Westphalians once again rose against their conquerors. The Eastphalians and Nordalbingians joined them in 793, but the insurrection did not catch on and was put down by 794. An Engrian rebellion followed in 796, but Charlemagne's personal presence and the presence of Christian Saxons and Slavs quickly crushed it. The last insurrection of the independence-minded people occurred in 804, more than thirty years after Charlemagne's first campaign against them. This time, the most unruly of them, the Nordalbingians, found themselves effectively disempowered from rebellion.

In 788, Charlemagne turned his attention to Bavaria. He claimed Tassilo was an unfit ruler on account of his oath-breaking. The charges were trumped up, but Tassilo was deposed anyway and put in the monastery of Jumièges. In 794, he was made to renounce any claim to Bavaria for himself and his family (the Agilolfings) at the synod of Frankfurt. Bavaria was subdivided into Frankish counties, like Saxony.

In 788, the Avars, a pagan Asian horde which had settled down in what is today Hungary (Einhard called them Huns), invaded Friuli and Bavaria. Charles was preoccupied until 790 with other things, but in that year, he marched down the Danube into their territory and ravaged it to the Raab. Then, a Lombard army under Pippin marched into the Drava valley and ravaged Pannonia. The campaigns would have continued if the Saxons had not revolted again in 792, breaking seven years of peace.

For the next two years, Charles was occupied with the Slavs against the Saxons. Pippin and Duke Eric of Friuli continued, however, to assault the Avars' ring-shaped strongholds. The great Ring of the Avars, their capital fortress, was taken twice. The booty was sent to Charlemagne at his capital, Aachen, and redistributed to all his followers and even to foreign rulers, including King Offa of Mercia. Soon the Avar tuduns had thrown in the towel and travelled to Aachen to subject themselves to Charlemagne as vassals and Christians. This Charlemagne accepted and sent one native chief, baptised Abraham, back to Avaria with the ancient title of khagan. Abraham kept his people in line, but in 800 the Bulgarians under Krum swept the Avar state away. In the 10th century, the Magyars settled the Pannonian plain and presented a new threat to Charlemagne's descendants.

In 789, in recognition of his new pagan neighbours, the Slavs, Charlemagne marched an Austrasian-Saxon army across the Elbe into Obotrite territory. The Slavs immediately submitted under their leader Witzin. Charlemagne then accepted the surrender of the Wiltzes under Dragovit and demanded many hostages and the permission to send, unmolested, missionaries into the pagan region. The army marched to the Baltic before turning around and marching to the Rhine with much booty and no harassment. The tributary Slavs became loyal allies. In 795, the peace broken by the Saxons, the Abotrites and Wiltzes rose in arms with their new master against the Saxons. Witzin died in battle and Charlemagne avenged him by harrying the Eastphalians on the Elbe. Thrasuco, his successor, led his men to conquest over the Nordalbingians and handed their leaders over to Charlemagne, who greatly honoured him. The Abotrites remained loyal until Charles' death and fought later against the Danes. Charlemagne also directed his attention to the Slavs to the south of the Avar khaganate: the Carantanians and Carniolans. These people were subdued by the Lombards and Bavarii and made tributaries, but never incorporated into the Frankish state.

In 799, Pope Leo III had been mistreated by the Romans, who tried to put out his eyes and tear out his tongue. Leo escaped, and fled to Charlemagne at Paderborn, asking him to intervene in Rome and restore him. Charlemagne, advised by Alcuin of York, agreed to travel to Rome, doing so in November 800 and holding a council on December 1. On 23 December Leo swore an oath of innocence. At Mass, on Christmas Day (25 December), when Charlemagne knelt at the altar to pray, the pope crowned him Imperator Romanorum ("Emperor of the Romans") in Saint Peter's Basilica. In so doing, the pope was effectively attempting to transfer the office from Constantinople to Charles. He used these circumstances to claim that he was the renewer of the Roman Empire, which had apparently fallen into degradation under the Byzantines. In his official charters from 801 onward, Charles preferred the style Karolus serenissimus Augustus a Deo coronatus magnus pacificus imperator Romanum gubernans imperium ("Charles, most serene Augustus crowned by God, the great, peaceful emperor ruling the Roman empire") to the more direct Imperator Romanorum ("Emperor of the Romans").

The Byzantines still held several territories in Italy: Venice (what was left of the Exarchate of Ravenna), Reggio (in Calabria), Brindisi (in Apulia), and Naples (the Ducatus Neapolitanus). These regions remained outside of Frankish hands until 804, when the Venetians, torn by infighting, transferred their allegiance to the Iron Crown of Pippin, Charles' son. The Pax Nicephori ended. Nicephorus ravaged the coasts with a fleet and the only instance of war between the Byzantines and the Franks, as it was, began. It lasted until 810, when the pro-Byzantine party in Venice gave their city back to the Byzantine Emperor and the two emperors of Europe made peace: Charlemagne received the Istrian peninsula and in 812 the emperor Michael I Rhangabes recognised his status as Emperor, although not necessarily as "Emperor of the Romans".

After the conquest of Nordalbingia, the Frankish frontier was brought into contact with Scandinavia. The pagan Danes, inhabiting the Jutland peninsula had heard many stories from Widukind and his allies who had taken refuge with them about the dangers of the Franks and the fury which their Christian king could direct against pagan neighbours. In 808, the king of the Danes, Godfred, built the vast Danevirke across the isthmus of Schleswig. This defence, last employed in the Danish-Prussian War of 1864, was at its beginning a 30 km (19 mi) long earthenwork rampart. The Danevirke protected Danish land and gave Godfred the opportunity to harass Frisia and Flanders with pirate raids. He also subdued the Frank-allied Wiltzes and fought the Abotrites. Godfred invaded Frisia and joked of visiting Aachen, but was murdered before he could do any more, either by a Frankish assassin or by one of his own men. Godfred was succeeded by his nephew Hemming, who concluded the Treaty of Heiligen with Charlemagne in late 811.

In 813, Charlemagne called Louis the Pious, king of Aquitaine, his only surviving legitimate son, to his court. There Charlemagne crowned his son with his own hands as co-emperor and sent him back to Aquitaine. He then spent the autumn hunting before returning to Aachen on 1 November. In January, he fell ill with pleurisy. He took to his bed on 21 January and died January twenty-eighth, the seventh day from the time that he took to his bed, at nine o'clock in the morning, after partaking of the Holy Communion, in the seventy-second year of his age and the forty-seventh of his reign. He was buried on the day of his death, in Aachen Cathedral, although the cold weather and the nature of his illness made such a hurried burial unnecessary.