Even though Canadian citizenship first appeared in 1947, athletes were recognised as Canadian as soon as the country was created in 1867.

The first Canadians to win a anything were the "Paris crew" who won a regatta days after the constitution. Canada started to be represented in the Olympic Games in 1900.

https://www.thecanadianencyclopedia.ca/en/article/paris-crew

https://en.wikipedia.org/wiki/Canada_at_the_1900_Summer_Olym...