The Battle of Dyrrhachium took place on October 18, 1081 between the Byzantine Empire, led by the Emperor Alexios I Komnenos (r. 10811118), and the Normans of southern Italy under Robert Guiscard, Duke of Apulia and Calabria. The battle was fought outside the city of Dyrrhachium (present-day Durrs in Albania), the major Byzantine stronghold in the western Balkans, and ended in a Norman victory.

Following the Norman conquest of Byzantine Italy and Saracen Sicily, the Byzantine emperor, Michael VII Doukas (r. 10711078), betrothed his son to Robert Guiscard's daughter. When Michael was deposed, Robert took this as an excuse to invade the Byzantine Empire in 1081. His army laid siege to Dyrrhachium, but his fleet was defeated by the Venetians. On October 18, the Normans engaged a Byzantine army under Alexios I Komnenos outside Dyrrhachium. The battle began with the Byzantine right wing routing the Norman left wing, which broke and fled. Varangian mercenaries joined in the pursuit of the fleeing Normans, but became separated from the main force and were massacred. Norman knights in the centre attacked the Byzantine centre and routed it, causing the bulk of the Byzantine army to rout.

After this victory, the Normans took Dyrrhachium in February 1082 and advanced inland, capturing most of Macedonia and Thessaly. Robert was then forced to leave Greece to deal with an attack on his ally, the Pope, by the Holy Roman Emperor, Henry IV (r. 10841105). Robert left his son Bohemond in charge of the army in Greece. Bohemond was initially successful, defeating Alexios in several battles, but was defeated by Alexios outside Larissa in 1083. Forced to retreat to Italy, Bohemond lost all the territory gained by the Normans in the campaign. The Byzantine recovery began the Komnenian restoration.

The Normans (Norman: Normaunds; French: Normands; Latin: Nortmanni/Normanni) were a population arising in the medieval Duchy of Normandy from the intermingling between Norse Viking settlers and indigenous West Franks and Gallo-Romans. The term is also used to denote emigrants from the duchy who conquered other territories such as England and Sicily. The Norse settlements in West Francia followed a series of raids on the French northern coast mainly from Denmark, although some also sailed from Norway and Sweden. Said settlements were finally legitimized when Rollo, a Scandinavian viking leader, agreed to swear fealty to King Charles III of West Francia following the siege of Chartres in 911 AD. The intermingling in Normandy produced an ethnic and cultural "Norman" identity in the first half of the 10th century, an identity which continued to evolve over the centuries.The Norman dynasty had a major political, cultural and military impact on medieval Europe and the Near East. The Normans were historically famed for their martial spirit and eventually for their Catholic piety, becoming exponents of the Catholic orthodoxy of the Romance community. The original Norse settlers adopted the Gallo-Romance language of the Frankish land they settled, with their Old Norman dialect becoming known as Norman, Normaund or Norman French, an important literary language which is still spoken today in parts of mainland Normandy (Cotentinais and Cauchois dialects) and the nearby Channel Islands (Jèrriais and Guernésiais). The Duchy of Normandy, which arose from the Treaty of Saint-Clair-sur-Epte, was a great fief of medieval France. The Norman dukes exercised independent control of their holdings in Normandy, while at the same time being vassals owing fealty to the King of France, and under Richard I of Normandy (byname "Richard sans Peur" meaning "Richard the Fearless") the Duchy was forged into a cohesive and formidable principality in feudal tenure. By the end of his reign in 996, the descendants of the Norse settlers "had become not only Christians but in all essentials Frenchmen. They had adopted the French language, French legal ideas, and French social customs, and had practically merged with the Frankish or Gallic population among whom they lived". Between 1066 and 1204, as a result of the Norman conquest of England, most of the kings of England were also dukes of Normandy. In 1204, Philip II of France seized mainland Normandy by force of arms, having earlier declared the Duchy of Normandy to be forfeit to him. It remained disputed territory until the Treaty of Paris of 1259, when the English sovereign ceded his claim to the Duchy, except for the Channel Islands. In the present day, the Channel Islands (the Bailiwick of Guernsey and the Bailiwick of Jersey) are considered to be officially the last remnants of the Duchy of Normandy, and are not part of the United Kingdom but are instead self-governing Crown Dependencies.The Normans are noted both for their culture, such as their unique Romanesque architecture and musical traditions, and for their significant military accomplishments and innovations. Norman adventurers played a role in founding the Kingdom of Sicily under Roger II after briefly conquering southern Italy and Malta from the Saracens and Byzantines, and an expedition on behalf of their duke, William the Conqueror, led to the Norman conquest of England at the historic Battle of Hastings in 1066. Norman and Anglo-Norman forces contributed to the Iberian Reconquista from the early eleventh to the mid-thirteenth centuries.Norman cultural and military influence spread from these new European centres to the Crusader states of the Near East, where their prince Bohemond I founded the Principality of Antioch in the Levant, to Scotland and Wales in Great Britain, to Ireland, and to the coasts of north Africa and the Canary Islands. The legacy of the Normans persists today through the regional languages and dialects of France, England, Spain, Quebec and Sicily, and also through the various cultural, judicial, and political arrangements they introduced in their conquered territories.