The Battle of Stilo (also known as Cape Colonna and Crotone) was fought on 13 or 14 July 982 near Crotone in Calabria between the forces of Holy Roman Emperor Otto II and his Italo-Lombard allies and those of the Kalbid emir of Sicily, Abu'l-Qasim. Some sources claim that the Muslims received support from the Byzantines, in retaliation for Otto's invasion of their province of Apulia, but this is unconfirmed.

Abu'l-Qasim, who had declared a Holy War (jihad) against the Germans, retreated when he noticed the unexpected strength of Otto's troops when he was not far from Rossano Calabro. Informed by some ships of the Muslim retreat, Otto left in that city his wife and children with the baggage and the imperial treasure, and set to pursue the enemy. When Abu'l-Qasim recognized that his flight had no hope of success, he fielded his army for a pitched battle south of Crotone at Cape Colonna. After a violent clash, a corps of German heavy cavalry destroyed the Muslim centre and pushed towards al-Qasim's guards. The emir was killed, but his troops were not shaken by the loss: they even managed to surround the German troops with a hidden cavalry reserve (approx. 5,000 warriors), slaughtering many of them. According to the historian Ibn al-Athir, casualties were around 4,000. Landulf IV of Benevento, Henry I, Bishop of Augsburg, Gnther, Margrave of Merseburg, the Abbot of Fulda and 19 other German counts were among them. Otto had to flee the battlefield and swim towards a Greek merchant ship which gave him shelter. Resting in Rossano, he only returned to Rome on 12 November 982.

The defeat forced Otto to flee north, where he held an assembly of primarily north Italian magnates at Verona. He sent his nephew Otto I, Duke of Swabia and Bavaria, back to Germany with the news, but he died en route. News of the battle did reach as far as Wessex, which is significant of the magnitude of the disaster. Bernard I of Saxony was heading south for the assembly when Danish Viking raids forced him to return. Saxon losses at Stilo had been most severe. At the assemblage, Otto secured his son Otto III's election as King of Italy and a call for reinforcements from Germany. He died the next year before continuing his campaign in the south.

The state of the Mezzogiorno was shaken up. Besides Landulf IV, his brothers Pandulf II of Salerno and Atenulf also died in battle. Though the Kalbid troops were forced to retreat afterwards to Sicily, the Saracens remained a presence in southern Italy, harassing the Greeks and Lombards. Capua and Benevento meanwhile passed to younger branches of the Landulfid family and Salerno was snatched by Manso, Duke of Amalfi.

In Germany, the Elbean Slavs, upon hearing news of the emperor's defeat, rose against their German suzerains under Mstivoj in a great revolt known as the Slawenaufstand. The Germanisation and Christianisation of the Slavs was put back for decades.

The Holy Roman Emperor, originally and officially the Emperor of the Romans (Latin: Imperator Romanorum, German: Kaiser der Römer) during the Middle Ages, and also known as the German-Roman Emperor since the early modern period (Latin: Imperator Germanorum, German: Römisch-deutscher Kaiser, lit. 'Roman-German emperor'), was the ruler and head of state of the Holy Roman Empire. The empire was considered by the Roman Catholic Church to be the only successor of the Roman Empire during the Middle Ages and the early modern period. The title was held in conjunction with the title of king of Italy (Rex Italiae) from the 8th to the 16th century, and, almost without interruption, with the title of king of Germany (Rex Teutonicorum, lit. “King of the Teutons”) throughout the 12th to 18th centuries.In theory and diplomacy, the emperors were considered primus inter pares, regarded as first among equals among other Roman Catholic monarchs across Europe.From an autocracy in Carolingian times (AD 800–924) the title by the 13th century evolved into an elective monarchy, with the emperor chosen by the prince-electors.

Various royal houses of Europe, at different times, became de facto hereditary holders of the title, notably the Ottonians (962–1024) and the Salians (1027–1125). Following the late medieval crisis of government, the Habsburgs kept possession of the title without interruption from 1440 to 1740. The final emperors were from the House of Habsburg-Lorraine, from 1765 to 1806. The Holy Roman Empire was dissolved by Francis II, after a devastating defeat by Napoleon at the Battle of Austerlitz.

The emperor was widely perceived to rule by divine right, though he often contradicted or rivaled the pope, most notably during the Investiture controversy. The Holy Roman Empire never had an empress regnant, though women such as Theophanu and Maria Theresa exerted strong influence. Throughout its history, the position was viewed as a defender of the Roman Catholic faith. Until Maximilian I in 1508, the emperor-elect (Imperator electus) was required to be crowned by the pope before assuming the imperial title. Charles V was the last to be crowned by the pope in 1530. Even after the Reformation, the elected emperor was always a Roman Catholic. There were short periods in history when the electoral college was dominated by Protestants, and the electors usually voted in their own political interest.