| Map: | Arguenon_cours_d'eau.png |
| Pushpin Map: | France#France Bretagne |
| Subdivision Type1: | Country |
| Subdivision Name1: | France |
| Subdivision Type2: | Region |
| Subdivision Name2: | Brittany |
| Subdivision Type3: | Department |
| Subdivision Name3: | Côtes-d'Armor |
| Source1 Location: | Le Gouray |
| Mouth: | English Channel |
| Mouth Location: | near Saint-Jacut-de-la-Mer |
| Tributaries Left: | Guébriand |
| Tributaries Right: | Rosette |
The Arguenon (in French pronounced as /aʁɡənɔ̃/; Breton: Argenon) is a French coastal river in the Côtes-d'Armor department of the Brittany region. It flows into the English Channel.
The length of the watercourse is .The river rises in the commune of Le Gouray in Côtes-d'Armor and flows into the sea near Saint-Jacut-de-la-Mer, in the commune of Créhen, in the Bay of Arguenon.The Arguenon is very wide between Jugon-les-Lacs and Plorec-sur-Arguenon. The Ville-Hatte dam built in 1972 to supply the department with drinking water has created a water reservoir more than long named Lac d'Arguenon.
The Arguenon runs northeast from its source to Jugon-les-Lacs, north between Jugon-les-Lacs and Plorec-sur-Arguenon, northeast again between Plorec-sur-Arguenon and Plancoët and north-northeast from Plancoët to its mouth.
During high tides a small tidal bore rises up the river, up to the height of the Guildo bridge.
The Arguenon's course is entirely within the Côtes-d'Armor department.It crosses twelve communes, from upstream to downstream: Le Gouray (source), Plénée-Jugon, Dolo, Jugon-les-Lacs, Plorec-sur-Arguenon, Plédéliac, Pléven, Bourseul, Pluduno, Plancoët, Saint-Lormel, Créhen and Saint-Cast-le-Guildo (mouth).
The managing body is SAGE Arguenon – Baie de la Fresnaye.
The Arguenon has four named tributary streams, one river and 10 unnamed tributaries including:
We can also add, according to the National Institute of Geographic and Forest Information or Géoportail, and since the Guébriand is not a river in its own right:
The Arguenon has been observed in Jugon-les-Lacs since 1972 at station J1103010 L'Arguenon, at an altitude of with a catchment area of 104km (65miles).The annual average of its flow at this point is .
At low water the minimum flow rate of the watercourse recorded for three consecutive days in a month, during a five-year dry period, was .
During the observation period, the maximum daily flow was observed on 28 February 2010 at . The maximum instantaneous flow (QIX: quantité instantanée maximale) was observed at 14:21 on 28 February 2010 was, and at the same time the instantaneous maximum height was .
The 10-year QIX is, the 20-year QIX is and the 50-year QIX is while the 2-year QIX is and the 5-year QIX is .
The Arguenon has experienced several significant floods. The first took place in 1974. The water overflowed on the Plancoët quay, causing major and widespread damage. The second took place in 2010, this time with on the quayside. The floodwater affected a lot of businesses. The last took place in February 2014, with on the quays. Shops were closed permanently and a park was completely flooded.
The depth of runoff in this part of the river's catchment area is annually, which is a little lower than the average in France. The specific flow rate reaches per of basin.
The Arguenon is crossed by Route nationale 176 and Route nationale 12.
The Arguenon estuary is protected by a Zone naturelle d'intérêt écologique, faunistique et floristique.
Arguenon Bay is part of the Natura 2000 zone Lancieux Bay, Arguenon Bay, Saint Malo and Dinard Archipelago.