structural:expansion
Modern era

The marriage of Anne of Brittany to Charles VIII of France in 1491 began the unification of the duchy of Brittany with the French crown which was ratified by Francis I of France in 1532. The union ended a long feudal conflict between France and Brittany, reasserting the king's suzerainty over the Bretons. In return for surrendering its independence, Brittany retained its privileges. Although most Breton institutions were maintained, the unification favoured Rennes (the site of ducal coronations). Rennes received most legal and administrative institutions, and Nantes kept a financial role with its Chamber of Accounts. During the French Wars of Religion from 1562 to 1598, the city was a Catholic League stronghold. The Duke of Mercœur, governor of Brittany, strongly opposed the succession of the Protestant Henry IV of France to the throne of France in 1589. The Duke created an independent government in Nantes, allying with Spain and pressing for independence from France. Despite initial successes with Spanish aid, in 1598 he submitted to Henry IV (who had by then converted to Catholicism); the Edict of Nantes (legalising Protestantism in France) was signed in the town, concluding the French wars of religion. Nonetheless, the town remained fervently Catholic (by contrast to nearby La Rochelle), and the local Protestant community did not number more than 1,000.

Coastal navigation and the export of locally produced goods (salt, wine and fabrics) dominated the local economy around 1600. During the mid-17th century, the siltation of local salterns and a fall in wine exports compelled Nantes to find other activities. Local shipowners began importing sugar from the French West Indies (Martinique, Guadeloupe and Saint-Domingue) in the 1640s, which became very profitable after protectionist reforms implemented by Jean-Baptiste Colbert prevented the import of sugar from Spanish colonies (which had dominated the market). In 1664 Nantes was France's eighth-largest port, and it was the largest by 1700. Plantations in the colonies needed labour to produce sugar, rum, tobacco, indigo dye, coffee and cocoa, and Nantes shipowners began trading African slaves in 1706. The port was part of the triangular trade: ships went to West Africa to buy slaves, slaves were sold in the French West Indies, and the ships returned to Nantes with sugar and other exotic goods. From 1707 to 1793, Nantes was responsible for 42 percent of the French slave trade; its merchants sold about 450,000 African slaves in the West Indies.

Manufactured goods were more lucrative than raw materials during the 18th century. There were about fifteen sugar refineries in the city around 1750 and nine cotton mills in 1786. Nantes and its surrounding area were the main producers of French printed cotton fabric during the 18th century, and the Netherlands was the city's largest client for exotic goods. Although trade brought wealth to Nantes, the city was confined by its walls; their removal during the 18th century allowed it to expand. Neoclassical squares and public buildings were constructed, and wealthy merchants built sumptuous hôtels particuliers.