Paris

The Parisii people inhabited the Paris area from around the middle of the 3rd century BC. One of the area's major north–south trade routes crossed the Seine on the Île de la Cité, which gradually became an important trading centre. The Parisii traded with many river towns, some as far away as the Iberian Peninsula, and minted their own coins.

Julius Caesar conquered the Paris Basin for the Roman Republic in 52 BC and began the Roman settlement on Paris's Left Bank. The Roman town was originally called Lutetia, more fully, Lutetia Parisiorum, "Lutetia of the Parisii", modern French Lutèce. It became a prosperous city with a forum, baths, temples, theatres, and an amphitheatre.

By the end of the Western Roman Empire, the town was known as Parisius, a Latin name that later became Paris in French. Christianity was introduced in the middle of the 3rd century AD by Saint Denis, the first Bishop of Paris: according to legend, when he refused to renounce his faith before the Roman occupiers, he was beheaded on the hill which became known as Mons Martyrum (Latin "Hill of Martyrs"), later "Montmartre", from where he walked headless to the north of the city; the place where he fell and was buried became an important religious shrine, the Basilica of Saint-Denis, and many French kings are buried there.

Clovis the Frank, the first king of the Merovingian dynasty, made the city his capital from 508. As the Frankish domination of Gaul began, there was a gradual immigration by the Franks to Paris, and the Parisian Francien dialects were born. Fortification of the Île de la Cité failed to avert sacking by Vikings in 845. Still, Paris's strategic importance—with its bridges preventing ships from passing—was established by successful defence in the Siege of Paris (885–886), for which the then Count of Paris (comte de Paris), Odo of France, was elected king of West Francia. From the Capetian dynasty that began with the 987 election of Hugh Capet, Count of Paris and Duke of the Franks (duc des Francs), as king of a unified West Francia, Paris gradually became the largest and most prosperous city in France.