Dux in the context of "Doge of Venice"

The Albanian nobility was an elite hereditary ruling class in Albania, parts of the western Balkans and later in parts of the Ottoman world. The Albanian nobility was composed of landowners of vast areas, often in allegiance to states like the Byzantine Empire, various Serbian states, the Republic of Venice, the Ottoman Empire and the Kingdom of Naples in addition to the Albanian principalities. They often used Byzantine, Latin or Slavic titles, such as sebastokrator, despot, dux, conte and župan. Notably, they also constructed religious sites, castles and had powerful courts. The Albanian principalities were usually divided in history except during the Principality of Arbanon when there was only one Albanian state ruled by one dynasty, and also during the League of Lezhë where most of the Albanian nobility and peasant communities unified under a military alliance against the Ottoman Empire.

Paristrion (Greek: Παρίστριον, lit. 'beside the Ister'), or Paradounabon/Paradounabis (Παραδούναβον / Παραδούναβις), which is preferred in official documents, was a Byzantine province covering the southern bank of the Lower Danube (Moesia Inferior) in the 11th and 12th centuries.

Although Byzantine authors use the term to describe the lands along the Danube in general, the province of Paristrion seems to have comprised mostly modern Dobruja. It is not certain exactly when the province was established: the Romanian scholar Nicolae Bănescu considered that it was established immediately after the end of the Rus'–Byzantine War of 970–971, while others, such as Vasil Zlatarski, thought it a later, mid-11th century creation. It was governed by a katepano or a doux, and was probably based at Dorostolon (modern Silistra), where a Byzantine strategia ("generalcy") is indeed attested in the 970s. In the aftermath of his victory over the Rus', Emperor John I Tzimiskes (r. 969–976) appointed general Leo Sarakenopoulos as commander over north-eastern Bulgaria, based at Pereyaslavets/Ioannopolis. Sarakenopoulos and his subordinates engaged in major fortification activities in the region of the Dobruja over the next few years, where abandoned Roman-era forts were rebuilt and re-occupied.

The Duchy of Rome (Latin: Ducatus Romanus; Greek: Δουκᾶτον Ῥώμης, romanized: Doukâton Rhṓmēs) was a state within the Byzantine Exarchate of Ravenna. Like other Byzantine states in Italy, it was ruled by an imperial functionary with the title of dux. The duchy often came into conflict with the Papacy over supremacy within Rome. After the founding of the Papal States in 756, the Duchy of Rome ceased to be an administrative unit and "dukes of Rome", appointed by the popes rather than emperors, are only rarely attested.

The Franks, Germanic peoples that invaded the Western Roman Empire in the 5th century, were first led by individuals called dukes and reguli. The earliest group of Franks that rose to prominence was the Salian Merovingians, who conquered most of Roman Gaul, as well as the Gaulish territory of the Visigothic Kingdom, following the Battle of Vouillé in 507 AD.

The sons of Clovis I, the first King of the Franks, conquered the Burgundian and the Alamanni Kingdoms. They acquired Provence, and went on to make the peoples of the Bavarii and Thuringii their clients. The Merovingians were later replaced by the new Carolingian dynasty in the 8th century. By the late 10th century, the Carolingians themselves had been replaced throughout much of their realm by other dynasties.

The Duchy of Amalfi (Latin: Ducatus Amalphitanus) or the Republic of Amalfi was a de facto independent state centered on the Southern Italian city of Amalfi during the 10th and 11th centuries. The city and its territory were originally part of the larger Duchy of Naples, governed by a patrician, but it extracted itself from Byzantine vassalage and first elected a duke (or doge) in 958.

During the 10th and 11th centuries Amalfi was estimated to have a population of 50,000–70,000 people. It rose to become an economic powerhouse, a commercial center whose merchants dominated Mediterranean and Italian trade in the ninth and tenth centuries, before being surpassed and superseded by the other maritime republics of the North and the Centre: Pisa, Venice, Genoa, Ancona and Gaeta. In 1073, Amalfi lost its independence, falling to Norman invasion and subsequently to Pisa in 1137.

The Duchy of Naples (Latin: Ducatus Neapolitanus, Neapolitan: Ducato di Napule) began as a Byzantine province that was constituted in the seventh century, in the lands roughly corresponding to the current province of Naples that the Lombards had not conquered during their invasion of Italy in the sixth century.

It was governed by a military commander (dux), and rapidly became a de facto independent state, lasting more than five centuries during the Early and High Middle Ages. Naples remains a significant metropolitan city in present-day Italy.

Duce (/ˈduːtʃeɪ/ DOO-chay, Italian: [ˈduːtʃe]) is an Italian title, derived from the Latin word dux, 'leader', and a cognate of duke. National Fascist Party leader Benito Mussolini was identified by Fascists as Il Duce ('The Leader') of the movement since the birth of the Fasci Italiani di Combattimento in 1919. In 1925 it became a reference to the dictatorial position of Sua Eccellenza Benito Mussolini, Capo del Governo, Duce del Fascismo e Fondatore dell'Impero ('His Excellency Benito Mussolini, Head of Government, Leader of Fascism and Founder of the Empire'). Mussolini held this title together with that of President of the Council of Ministers: this was the constitutional position which entitled him to rule Italy on behalf of the king of Italy. Founder of the Empire was added for the exclusive use by Mussolini in recognition of his founding of an official legal entity of the Italian Empire on behalf of the king in 1936 following Italy's victory in the Second Italo-Ethiopian War. The position was held by Mussolini until 1943, when he was removed from office by the king and the position of Duce was discontinued, while Marshal Pietro Badoglio was appointed Presidente del Consiglio.

This position was the model which other fascist leaders adopted, such as the position of Führer by Adolf Hitler and Caudillo by Francisco Franco. In September 1943, Mussolini styled himself as the "Duce of the Italian Social Republic" (Italian: Duce della Repubblica Sociale Italiana), and held the position until the collapse of the Italian Social Republic and his execution in April 1945.