|Yamaska River at Saint - Hyacinthe - Gregory Lussier|
Sourcing water within the Eastern Townships, it ends its journey in Lake Saint-Pierre where it is a tributary to the Saint Lawrence River; altogether it is 177 km (110 mi) long. Crossing nearly twenty municipalities in its course, it is intrinsically linked to life around it as it is a primary source of fresh water where it passes; due to human use and adaptation, the river and its banks have become heavily altered over time, beginning around the time the first European settlers arrived to modern days.
The name Yamaska appeared in the 17th century, beforehand it was named "Rivière de Gennes" (French for River of Gennes) by Samuel de Champlain in 1609. When the lands known as seigneurie de Yamaska were granted to Michel Leneuf de La Vallière, the river's name was instead "rivière des Savanes".
The word "Yamaska" could be sourced to Abenakis meaning "there are rushes off the coast" or "there is much hay", from yam or iyamitaw, respectively meaning off shore and much, and askaw, meaning hay or rushes.
This Amerindian name references baie de Lavalilière (Lavallière Bay), at the river's mouth where vegetation grows abundantly in a marsh. The name could also be from Algonquian hia muskeg, it means "river of the savannas" or "river with muddy waters".
Because of the nebulous Amerindian origin, this naming has been deformed (often in the form of Maska or Masca, after which the inhabitants of Saint-Hyacinthe are named). It was officially named Rivière Yamaska 5 December 1968.