The Pont de l'Iroise is a cable-stayed bridge in Finistère, Brittany, France, which spans the Élorn river where it enters the roadstead of Brest. It carries route nationale 165, the road between Brest and Quimper, and connects Le Relecq-Kerhuon to the north with Plougastel-Daoulas to the south. The bridge is named after the Iroise Sea, into which the roadstead of Brest opens.
Iroise or the Iroise Sea (French: mer d'Iroise, pronounced: [i.ʁwɑz] or [i.ʁwa]) is the part of the Atlantic Ocean which stretches from the Ile de Sein to Ushant off the coast of Brittany in north-western France. It borders the Celtic Sea to the north and west and the Bay of Biscay to the south. It is one of the most dangerous seas in Europe. In winter, there are often violent storms with huge waves. But it is also considered to be one of the richest areas for marine life leading to its inclusion as one of UNESCO's biosphere reserves in 1988 and as France's first marine park in October 2007.
The name is first recorded in the Neptune francois of 1693 as Le Passage de l'Yroise (passage = "channel"); as Passage de l'Iroise in the 18th century; as Iroise in the 19th century; and as mer d'Iroise (mer = "sea") in the 1970s, by the seabed exploration industry. The name appears to have been fixed not by local seafarers but rather by the naval base at Brest. The 18th-century maps restrict "Passage de l'Iroise" to the channel leading north-west from Pointe Saint-Mathieu and keeping south of Ushant and the Ponant Islands. From the 19th century, Iroise encompasses all the sea the west coast of Brittany, between Ouessant and Sein. While this remains the limit used by mariners, some twentieth-century sources have used mer d'Iroise to denote the entire Celtic Sea as far as Ireland and England.