Cyr was born on the 10th of October 1863 in the lower region of Canada in a town called Saint-Cyprien also known as Napierville. He was the second born of seventeen children.
When he was a child, Louis Cyr was quick witted, wilful yet still gentle by nature. From his early years, it was clear that Louis had exceptional strength that he apparently got from his paternal grandfather named Pierre Cyr, who was a trapper and a hunter. Louis also got some strongman genes from his mother who was a woman of great physical stature and ability.