May– A Norman fleet of 150 ships (including 60 horse transports), led by Duke Robert Guiscard, sets off towards the Dalmatian coast. An army of 15,000 men (including about 1,300 Norman knights) sails to the city of Avalona (modern Albania); they are joined by several ships from Ragusa, a republic in the Balkans who are enemies of the Byzantines.
October 18–Battle of Dyrrhachium: After taking the island of Corfu, Robert Guiscard advances to Dyrrhachium (modern-day Durrës), and lays siege to the city. Alexios I Komnenos attempts to defend Illyria from the Normans (the first recorded mention of Albania), but is defeated by Guiscard, outside Dyrrhachium, the Byzantine capital city of Illyria.
Seljuk emir Tzachas (or Chaka Bey) conquers Smyrna (modern-day İzmir) and founds a short-lived independent state, which emerges as the first sea power in Turkish history.
Spring – The Normans under Duke Robert Guiscard take Dyrrhachium (modern-day Durrës) in Illyria and advance inland, capturing most of Macedonia and Thessaly. Robert is forced to leave Greece to deal with an uprising in Italy. He leaves his son Bohemond in charge of the army, who lays siege to the city of Larissa. Emperor Alexios I Komnenos mobilizes a new army, and with the support of 7,000 Seljuk Turks he clears Thessaly from the Normans.
Winter –Henry IV, Holy Roman Emperor, leads an expedition into Italy and besieges Rome. He gains entry and a synod is agreed upon by the Romans to rule on the dispute between Henry and Pope Gregory VII.
Adalbero, margrave of Styria, is forced to resign in favor of his brother Ottokar II, who is an ally of Gregory VII.
The first mention of the town of Hofgeismar (modern Germany) is recorded.
Asia
Approximate date – The Korean printing of the entire BuddhistTripiṭaka is completed.
January 6– A Castilian army, under Count Gonzalo Salvadórez and his son-in-law Ramiro Garcés, Lord of Calahorra, child of the late King García Sánchez III of Pamplona, enters the surrendered bastion of Rueda, but are then treacherously set upon and killed. Gonzalo, Ramiro, and Ramiro's illegitimate half-brother Sancho Garcés are among the many nobles to lose their lives, in what will be remembered as the 'disaster' or 'treachery of Rueda'.
October – While Robert Guiscard is in Italy, emperor Alexios I Komnenos retakes territory previously lost to the Normans, including the town of Kastoria. Several Normans, including Peter Aliphas, switch sides to the Byzantines.
March 31– Emperor Henry IV besieges Rome and enters the city. He is crowned Holy Roman Emperor by Antipope Clement III in Rome and receives the patrician authority.
May–Sack of Rome: Duke Robert Guiscard leads a Norman army (36,000 men) north and enters Rome; the city is sacked, and Henry IV is forced to retreat.
Pope Gregory VII, who has been forced by the presence in Rome of Henry IV to retreat to the Castel Sant'Angelo, is freed by Robert Guiscard and restores papal authority in Rome.
The Domesday Survey is commissioned by King William the Conqueror, apparently prompted by the abortive invasion of Canute IV, to ensure proper taxation and levies.
China
April 1–Emperor Zhezong ascends the throne at the age of 8 under the supervision of his grandmother, Grand Empress Dowager Gao. She cancels the reform policy of Chancellor Wang Anshi.
The output of copper currency for the Chinese Song dynasty reaches 6 billion coins a year, prompting the Chinese government to adopt the world's first paper-printed money later in the 1120s.
August 1– King William the Conqueror calls for a meeting at Old Sarum, where he invites his major vassals and tenants-in-chief to swear allegiance to him. This is known as the Oath of Salisbury.
The Domesday Book is completed. Drawn up on the orders of William I; it describes in detail the landholdings and resources in England.
The population in England is estimated to be 1.25 million citizens with 10% living in boroughs.
Summer – The Taifa of Valencia falls under the domination of El Cid. He stabilizes the region around Valencia, which has revolted against the Moorish puppet ruler Al-Qadir.
Inge the Elder returns to Svealand and kills his brother-in-law Blot-Sweyn after a 3-year reign. Inge again proclaims himself king of Sweden (approximate date).
Mahdia campaign: The navies of Genoa and Pisa take the capital of the Zirids, and occupy Mahdia for a year. Subsequently, both republics obtain trading privileges.
January 3– Emperor Shirakawa abdicates in favor of his 7-year-old son Horikawa after a 14-year reign. He exerts his personal power to set the cloistered rule system further in motion.
Middle East
May: The marriage of Caliph al-Muqtadi and Mah-i Mulk is consummated. This marriage strengthens the political relation of Malik-Shah I and the Caliph.
By topic
Religion
May 9– The relics of Saint Nicholas, patron saint of seafarers, are stolen by Italian sailors from his church in Myra (modern Turkey) and transported to Bari in southern Italy.
The Worcestershire rebellion led by Robert de Lacy (a son of Ilbert de Lacy) is dealt with quickly by Wulfstan, bishop of Worcester, who calls on those knights and local landowners still loyal to William II to defend Worcester. Many of the rebels are captured or killed.
William II calls the representatives of the fyrd to a meeting in London. He promises (with the support of Lanfranc, bishop of Canterbury) the people better laws, and the removal of taxes if they support him against the rebels.
William II lays siege to Pevensey Castle on the south coast where Odo of Bayeux has taken shelter with Robert. Odo is forced to surrender, and agrees to go to Rochester to convince the rebels to accept William as the rightful king of England.
Summer – William II lays siege to Rochester Castle and puts down the revolt. Odo of Bayeux and the rebels surrender (agreeing only that their lives will be spared). William takes Odo's lands and exiles him to Normandy.
Su Song, Chinese polymath scientist and statesman, invents the pilot model for his astronomicalclock tower constructed in Kaifeng. It features an escapement mechanism – and the world's oldest known power-transmitting chain drive to operate the armillary sphere, opening doors, and mechanical-driven mannequins, that would rotate in shifts to announce the time on plaques.
August 28–Braga Cathedral in the County of Portugal has its reconstruction (following 353 years of Muslim occupation) completed sufficiently for its consecration to the Virgin Mary to take place.