The Semnon (; br, Sevnon) is a long river in the

Mayenne Mayenne () is a landlocked department in northwest France named after the river Mayenne. Mayenne is part of the administrative region of Pays de la Loire and is surrounded by the departments of Manche, Orne, Sarthe, Maine-et-Loire, and Ille-et ...

Maine-et-Loire Maine-et-Loire () is a department in the Loire Valley in the Pays de la Loire region in Western France. It is named after the two rivers, Maine and the Loire. It borders Mayenne and Sarthe to the north, Loire-Atlantique to the west, Indre-e ...

Ille-et-Vilaine Ille-et-Vilaine (; br, Il-ha-Gwilen) is a department of France, located in the region of Brittany in the northwest of the country. It is named after the two rivers of the Ille and the Vilaine. It had a population of 1,079,498 in 2019.

and

Loire-Atlantique Loire-Atlantique (; br, Liger-Atlantel; before 1957: ''Loire-Inférieure'', br, Liger-Izelañ, link=no) is a department in Pays de la Loire on the west coast of France, named after the river Loire and the Atlantic Ocean. It had a population o ...

départements A department (, ) is an administrative or political division in several countries. Departments are the first-level divisions of 11 countries, nine in the Americas and two in Africa. An additional 10 countries use departments as second-level div ...

'', northwestern France. Its source is at Congrier. It flows generally west-northwest. It is a

left tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage b ...

of the

Vilaine The Vilaine (; br, Gwilen) is a river in Brittany, in the west of France. The river's source is in the Mayenne ''département'' (53), and it flows out into the Atlantic Ocean at Pénestin in the Morbihan ''département'' (56). It is 218 km ...

into which it flows between Pléchâtel and

Bourg-des-Comptes Bourg-des-Comptes (; br, Gwikomm; Gallo: ''Bórg-Cons'') is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The river Semnon forms all of the commune's southern border, then flows into the Vilaine, whi ...

''Départements'' and communes along its course

This list is ordered from source to mouth: *Mayenne: Congrier, Saint-Erblon, Senonnes *Maine-et-Loire:

Pouancé Pouancé () is a former commune in the Maine-et-Loire department in western France. On 15 December 2016, it was merged into the new commune Ombrée d'Anjou. It is located on the border of 4 French departements: Maine-et-Loire, Mayenne in the n ...

*Ille-et-Vilaine:

Eancé Eancé (; br, Aentieg) is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The river Semnon flows northwest through the commune. Population Inhabitants of Eancé are called ''Éancéens'' in French. ...

Martigné-Ferchaud Martigné-Ferchaud (; ; Gallo: ''Marteinyaé-Fèrchaud'') is a commune in the Ille-et-Vilaine department of Brittany in northwestern France. Etymology The name "Martigné" is thought to date from the Gallo-Roman period, the place being named af ...

*Loire-Atlantique:

Fercé Fercé (; br, Ferreg) is a commune in the Loire-Atlantique department in western France. Geography The Semnon forms part of the commune's northern border; the Brutz, a tributary of the Semnon, forms all of its southern border. Fercé is also loc ...

*Ille-et-Vilaine:

Thourie Thourie (; br, Tourig) is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The '' ruisseau de la Couyère'' forms all of the commune's western border, then flows into the Semnon, which forms all of its ...

*Loire-Atlantique:

Soulvache Soulvache (; br, Soulvac'h) is a commune in the Loire-Atlantique department in western France. Geography The Brutz forms all of the commune's western border, then flows into the Semnon The Semnon (; br, Sevnon) is a long river in the Mayenn ...

*Ille-et-Vilaine:

Teillay Teillay (; br, Tilheg) is a Communes of France, commune in the Ille-et-Vilaine Departments of France, department in Brittany (administrative region), Brittany in northwestern France. Geography The Brutz forms all of the commune's eastern border, ...

Ercé-en-Lamée Ercé-en-Lamée (, literally ''Ercé in Lamée''; ) is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The river Semnon forms all of the commune's northern border. Population Inhabitants of Ercé-en ...

, Lalleu,

Tresbœuf Tresbœuf (; br, Trevo) is a commune in the Ille-et-Vilaine department of Brittany in northwestern France. Geography The river Semnon forms part of the commune's southern border. Population People from Tresbœuf are called ''tresbourgeois'' i ...

La Bosse-de-Bretagne La Bosse-de-Bretagne (; ; Gallo: ''La Bocz'') is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The river Semnon forms most of the commune's southern border. Population Inhabitants of La Bosse-de-B ...

Bain-de-Bretagne Bain-de-Bretagne (, Gallo: ''Bóen'') is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Geography The river Semnon forms part of the commune's northern boundary. Population Inhabitants of Bain-de-Bretagne ar ...

Pancé Pancé (; br, Pantieg; Gallo: ''Panczaé'') is a commune in the Ille-et-Vilaine department of Brittany in northwestern France. Geography The river Semnon forms all of the commune's southern border. Population Inhabitants of Pancé are called ...

, Pléchâtel, Poligné,

References

Rivers of France Rivers of Loire-Atlantique Rivers of Ille-et-Vilaine Rivers of Mayenne Rivers of Maine-et-Loire Rivers of Pays de la Loire Rivers of Brittany {{France-river-stub