Canada competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Canadian athletes have competed in every Summer Olympic Games since 1900, except the 1980 Summer Olympics in Moscow because of the country's support for the US-led boycott.

Canada competed at the 1904 Summer Olympics in St. Louis, United States. These Games were the second at which Canadian athletes participated. As in 1900 they did not compete under the Canadian flag, national teams not being introduced until the next Olympics. Unofficially, however, it was a very successful Olympics for Canada with Canadian competitors winning the fourth most medals. However, this was largely because most Europeans decided not to make the long trip to compete in the games. The Canadian athletes were a unified group for the first time and were unofficially regarded as a team.