| Saint-Cyr | |
| Map: | Ottawarivermap.png |
| Subdivision Type1: | Country |
| Subdivision Name1: | Canada |
| Subdivision Type2: | Province |
| Subdivision Name2: | Quebec |
| Subdivision Type3: | Region |
| Subdivision Name3: | Outaouais |
| Length: | 25km (16miles)[1] |
| Source1: | La Truite Lake |
| Source1 Location: | Rapides-des-Joachims, Quebec, Pontiac Regional County Municipality (RCM), Outaouais, Quebec |
| Source1 Coordinates: | 46.3397°N -77.6064°W |
| Source1 Elevation: | 362m (1,188feet) |
| Mouth: | Ottawa River |
| Mouth Location: | Sheenboro, Quebec, Pontiac Regional County Municipality (RCM), Outaouais, Quebec |
| Mouth Coordinates: | 46.1819°N -77.6278°W |
| Mouth Elevation: | 120m (390feet) |
The Saint-Cyr River is a tributary of the eastern shore of the Ottawa River. The Saint-Cyr River flows into the Municipality Rapides-des-Joachims, then from Sheenboro into the Regional County Municipality (MRC) Pontiac Regional County Municipality, in Outaouais administrative region, in Quebec, in Canada.
The former name of the river was "Boom West Brook", as opposed to the branch being referred to as "Boom Creek" in this hydrographic slope.
The toponym "Saint-Cyr River" was formalized on December 5, 1968, at the Commission de toponymie du Québec.[2]