Rennes is a city in the east of Brittany in Northwestern France at the confluence of the rivers Ille and Vilaine. Rennes is the prefecture of t…Rennes is a city in the east of Brittany in Northwestern France at the confluence of the rivers Ille and Vilaine. Rennes is the prefecture of the Brittany region and Ille-et-Vilaine department. In 2017, its urban area had a population of 357,327 inhabitants, while the larger metropolitan area had a population of 739,974. The inhabitants of Rennes are called Rennais and Rennaises in French.