Iroise () or the Iroise Sea ( ; ) is the part of the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

which stretches from the Ile de Sein to

Ushant Ushant (; , ; , ) is a French island at the southwestern end of the English Channel which marks the westernmost point of metropolitan France. It belongs to Brittany and in medieval times, Léon. In lower tiers of government, it is a commune in t ...

off the coast of

Brittany Brittany ( ) is a peninsula, historical country and cultural area in the north-west of modern France, covering the western part of what was known as Armorica in Roman Gaul. It became an Kingdom of Brittany, independent kingdom and then a Duch ...

in north-western

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. It is contained within the

Celtic Sea The Celtic Sea is the area of the Atlantic Ocean off the southern coast of Ireland bounded to the north by St George's Channel, Saint George's Channel; other limits include the Bristol Channel, the English Channel, and the Bay of Biscay, as wel ...

, bordering the remainder of the Celtic Sea to the north and west, and the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

to the south. It is one of the most dangerous seas in Europe for sea-going vessels. In winter, there are often violent storms with huge waves. It is also one of the richest areas for

marine life Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, aquatic plant, plants, algae, marine fungi, fungi, marine protists, protists, single-celled marine microorganisms, microorganisms ...

and was designated as one of

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

biosphere reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...

s in 1988 and as France's first

marine park A marine park is a designated park consisting of an area of sea (or lake) set aside to achieve ecological sustainability, promote marine awareness and understanding, enable marine recreational activities, and provide benefits for Indigenous peo ...

in October 2007.

Name and extent

The name is first recorded in the ''Neptune francois'' of 1693 as ''Le Passage de l'Yroise'' ( = "

channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Australia in Queensland and pa ...

"); as Passage de l'Iroise in the 18th century; as Iroise in the 19th century; and as mer d'Iroise ( = "sea") in the 1970s, by the seabed exploration industry. The name appears to have been fixed not by local seafarers but rather by staff at the naval base at Brest. The 18th-century maps identify "Passage de l'Iroise" as the channel leading north-west from Pointe Saint-Mathieu and keeping south of Ushant (Ouessant) and the Ponant Islands. From the 19th century, the term ''Iroise'' encompassed all the sea along 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

as far as Ireland and Great Britain. The meaning of ''Iroise'' is obscure; theories include: * from the

Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th

* from a dubious Old French adjective ''iroise,'' meaning "angry", referring to the rough seas (sometimes ''Angry Sea'' is found as an English language translation) * from Breton language">Breton Breton most often refers to: *anything associated with Brittany, and generally **Breton people **Breton language, a Southwestern Brittonic Celtic language of the Indo-European language family, spoken in Brittany ** Breton (horse), a breed **Gale ...

''hirgwaz''; ''hir'' "long" + ''gwaz'' "stream, channel" * From the Breton ''ervoas,'' or "deep", referring to the Atlantic Ocean, in contrast to the shallow English Channel From the 1990s, "Iroise" became popular in Finistère in the name of many local businesses and associations. The Pont de l'Iroise bridge was opened in 1994. in Marine weather forecasting, maritime weather forecasts by [ étéo-France and Spain's

AEMET The State Meteorological Agency (, AEMET) is a state agency of the Government of Spain responsible for providing weather forecast, warnings of hazardous weather and assisting the administrations in such matters. The AEMET is part of the Secretari ...

, "Iroise" denotes the sea area east of a line from to ; this corresponds to the northern part of the UK shipping forecast sea area of

Biscay Biscay ( ; ; ), is a province of the Basque Country (autonomous community), Basque Autonomous Community, heir of the ancient Lordship of Biscay, lying on the south shore of the Bay of Biscay, eponymous bay. The capital and largest city is Bilb ...

Location and environment

The Iroise coastline consists of a rich variety of beaches, rocky cliffs, sand dunes, coves and islands such as the

Île de Sein The Île de Sein is a Breton island in the Atlantic Ocean, off Finistère, eight kilometres from the Pointe du Raz (''raz'' meaning "water current"), from which it is separated by the Raz de Sein. Its Breton name is ''Enez-Sun''. The islan ...

and the Island of Molene. The considerable differences in depth and the adjacent

English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...

create the strong currents through the Iroise. High tides in the Channel bring about strong north-easterly currents, which reverse at low tide. The currents can reach particularly high speeds at the

Raz de Sein The Raz de Sein is a stretch of water located between the Isle of Sein and the Pointe du Raz in Finistère located in the Brittany region of France. This tidal water is an essential passage for vessels wishing to pass between the Atlantic and t ...

or the

Goulet de Brest The Goulet de Brest (; ) is a 3-km-long strait linking the roadstead of Brest to the Atlantic Ocean. Only 1.8 km wide, the is situated between the Pointe du Petit Minou and the Pointe du Portzic to the north and the îlot des Capucins and t ...

. Many lighthouses were erected in the area to guide sailors. Many local legends describe lost ships and tragedies at sea.

Activities

The Iroise Sea enjoys a variety of activities. The

French navy The French Navy (, , ), informally (, ), is the Navy, maritime arm of the French Armed Forces and one of the four military service branches of History of France, France. It is among the largest and most powerful List of navies, naval forces i ...

has been active there since 1631, when Brest was established as a

naval base A naval base, navy base, or military port is a military base, where warships and naval ships are docked when they have no mission at sea or need to restock. Ships may also undergo repairs. Some naval bases are temporary homes to aircraft that usu ...

. Since the late 20th century, it has been a centre of submarine activity, owing to the

nuclear submarine A nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed. Nuclear submarines have considerable performance advantages over "conventional" (typically diesel-electric) submarines. Nuclear propulsion ...

base established at

Île Longue Île Longue (; French language, French for "Long Island"; ) is a peninsula of the roadstead of Brest in the department of Finistère in the Brittany region. It is the base of the French SSBN, nuclear ballistic missile submarines (), and as such ...

on the

Crozon Crozon (, ; , , ) is a commune in the department of Finistère and the administrative region of Brittany, northwestern France. As well as the town of Crozon, the village of Morgat is part of the commune. Crozon is located on the Crozon penin ...

peninsula in the

roadstead of Brest The roadstead of Brest (, ; ) is a roadstead or bay located in the Finistère Departments of France, department in Brittany (administrative region), Brittany in northwestern France. The surface area is about 180 km² (70 sq mi). The po ...

. Fishing, though less important than in the past, is still practised, especially through the ports of

Le Conquet Le Conquet (; ) is a commune in the Finistère department of Brittany in northwestern France. This is the westernmost town of mainland France. Only three island towns—Ouessant, Île-Molène and Ile de Sein—are farther west. Maritime tran ...

Douarnenez Douarnenez (, ; meaning ''douar'' (land) ''an enez'' (the island) or land of the island), is a commune in the French department of Finistère, region of Brittany, northwestern France. It is located at the mouth of the Pouldavid River, an estua ...

, Camaret and Brest. Catches range from

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s to

sardine Sardine and pilchard are common names for various species of small, oily forage fish in the herring suborder Clupeoidei. The term "sardine" was first used in English during the early 15th century; a somewhat dubious etymology says it com ...

s and

monkfish Members of the genus ''Lophius'', also sometimes called monkfish, fishing-frogs, frog-fish, and sea-devils, are various species of lophiid anglerfishes found in the Atlantic and Indian Oceans. ''Lophius'' is known as the "monk" or "monkfish" to ...

. The area is also popular for sailing and pleasure boating, particularly in the less exposed areas along the coast and in

Douarnenez Bay The Baie de Douarnenez (; ) is a bay in Finistère, France, between the Crozon Peninsula to the north and the Cap Sizun to the south. It is a vast semi-circular basin over wide and from its entrance to the opposite shore. Although half closed o ...

. Diving is also increasingly popular, particularly in view of the many accessible wrecks and spectacular underwater vistas.

Sea search and rescue

Owing to the hazardous conditions at sea, the high density of shipping and a number of shipwrecks in recent years, the French authorities have introduced special

search and rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...

operations. These rely on vessels such as the ''

Abeille Bourbon ''Abeille Bourbon'', whose name was changed to ''Abeille Bretagne'' in 2025, is a high seas emergency tow vessel (salvage tug), long with a tractive power of , a crew of 12, designed by Norwegian naval architect Sigmund Borgundvåg. She was ch ...

,'' as well as a number of large lifeboats based in the ports of

, Camaret,

Molène Molène or Molene (; , "Bald Island") is an islands of France, island in the Atlantic Ocean, Atlantic off the west coast of Brittany in northwestern France. It is the largest of Molène or Molene Archipelago (), a group of about 20 islands in the ...

and

Marine Park

Despite several major

oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

s and cases of

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

, the Iroise Sea is still rich in flora and fauna. It is especially well known for its seabass, its shoals of

dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

seals Seals may refer to: * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to impress an emblem, used as a means of a ...

lobster Lobsters are Malacostraca, malacostracans Decapoda, decapod crustaceans of the family (biology), family Nephropidae or its Synonym (taxonomy), synonym Homaridae. They have long bodies with muscular tails and live in crevices or burrows on th ...

s and, on occasion, sunfish,

basking shark The basking shark (''Cetorhinus maximus'') is the second-largest living shark and fish, after the whale shark. It is one of three Planktivore, plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sh ...

and

whale Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...

s. The many varieties of seabird include

cormorants Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the International Ornithologists' Union (IOU) ado ...

guillemot Guillemot is the common name for several species of seabird in the Alcidae or auk family, part of the order Charadriiformes. In Europe, the term covers two genera, '' Uria'' and '' Cepphus''. In North America the ''Uria'' species are called mu ...

s and

herons Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus '' Botaurus'' are referred to as ...

. The sea is also recognized as the richest environment for

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

in Europe, with some 300 species. As a result, on 2 October 2007, the French authorities designated this area as the country's first marine park, officially labelled ''Parc naturel marin d'Iroise.'' Its three main objectives are to increase knowledge of the marine environment, to protect the area's habitats and species, and to develop marine activities of all kinds. The Iroise Marine Park covers an area of from latitude 48°31′N (the north coast of

) and latitude 47°59′N (south coast of the

), the mainland coastline to the east except for the Rade de Brest, and the limit on French

territorial waters Territorial waters are informally an area of water where a sovereign state has jurisdiction, including internal waters, the territorial sea, the contiguous zone, the exclusive economic zone, and potentially the extended continental shelf ( ...

to the west.

Ecology

The Iroise Sea is among the world's most important

biogeographic Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

transition zones. This is a dividing line between the

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

marine and the cold-temperate and

boreal Boreal, northern, of the north. Derived from the name of the god of the north wind from Ancient Greek civilisation, Boreas (god), Boreas. It may also refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernand ...

marine animals.

References

{{Coord, 48, 13, N, 04, 48, W, region:FR_scale:500000, display=t Landforms of Brittany Marginal seas of the Atlantic Ocean Seas of France Marine parks of France Biosphere reserves of France