Saint-Denis, town, capital of the French overseas département of Réunion in the western Indian Ocean. The town lies in a basin at the mouth of the Saint-Denis River on the north coast of the island, wedged between the ocean and a mountain rising abruptly behind it. It was originally the main port of Réunion, but an artificial harbour at Le Port, on the northwest coast, replaced it in the 1880s, because of unpredictable winds and tides at Saint-Denis. The two are connected by 12 miles (20 km) of scenic highway along the coast. Saint-Denis is primarily an administrative town. An international airport, several libraries, a natural history museum, and a university for the study of law, economics, and political science are located there.