If you come from the following countries, you will require a visitor's visa AND a student authorisation/visa to study in Canada (Note: language study programs under three month's in length do not require a student authorisation):

http://www.cic.gc.ca/english/visit/visas_e.html

Citizens of the following countries require a Visa to VISIT or TRANSIT Canada:
A Afghanistan, Albania, Algeria, Angola, Argentina, Armenia, Azerbaijan B Bahrain, Bangladesh, Belarus, Belize, Benin, Bhutan, Bolivia, Bosnia-Hercegovina, Brazil, Bulgaria, Burkina-Faso, Burundi C Cambodia, Cameroon, Cape Verde, Central African Republic, Chad, Chile, China, People's Republic Colombia, Comoros, Congo (The), Democratic Republic of Congo (The), People's Republic of Croatia, Cuba, Czech Republic D Djibouti, Dominican Republic E Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea, Estonia, Ethiopia F Fiji G Gabon, Gambia, Georgia, Ghana, Guatemala, Guinea, Guinea-Bissau, Guyana H Haiti, Honduras I India, Indonesia, Iran, Iraq Israel (only Israeli citizens holding valid Israeli orange "Travel Document in Lieu of National Passport"), Ivory Coast J Jamaica, Jordan, K Kazakhstan, Kenya, Korea, North Kuwait, Kyrgyzstan L Laos, Latvia, Lebanon, Lesotho, Liberia, Libya, Lithuania M Macedonia (former Yugoslav Republic of), Malagasy Republic, Malawi, Maldives, Mali, Mauritania, Mauritius, Moldova, Mongolia, Morocco, Mozambique, Myanmar (Burma) N Nepal, Nicaragua, Niger, Nigeria O Oman P Pacific Islands- U.S. Trust Territory, Pakistan, Panama, Paraguay, Peru, Philippines, Poland Q Qatar R Romania, Russia, Rwanda S Sao Tome e Principe, Senegal, Seychelles (The), Sierra Leone, Slovak Republic, Somalia, South Africa, Sri Lanka, Sudan, Surinam, Syria T Tadjikistan, Taiwan, Tanzania, Thailand, Togo, Tonga, Trinidad and Tobago, Tunisia, Turkey, Turkmenistan U Uganda, Ukraine, United Arab Emirates, Uruguay, Uzbekistan V Venezuela, Vietnam Y Yemen, Yugoslavia Z Zambia

Vistor Visa Exemptions
Many people do not require a visa to visit Canada.

These include:
Citizens of Andorra, Antigua and Barbuda, Australia, Austria, Bahamas, Barbados, Belgium, Botswana, Brunei, Costa Rica, Cyprus, Denmark, Dominica, Finland, France, Germany, Greece, Grenada, Hungary, Iceland, Ireland, Israel (National Passport holders only), Italy, Japan, Kiribati, Liechtenstein, Luxembourg, Malaysia, Malta, Mexico, Monaco, Namibia, Nauru, Netherlands, New Zealand, Norway, Papua New Guinea, Portugal, Republic of Korea, St. Kitts and Nevis, St. Lucia, St. Vincent, San Marino, Saudi Arabia, Singapore, Solomon Islands, Spain, Swaziland, Sweden, Slovenia, Switzerland, Tuvalu, United States, Vanuatu, Western Samoa and Zimbabwe;

• Persons lawfully admitted to the United States for permanent residence who are in possession of their alien registration card (Green card) or can provide other evidence of permanent residence.

• British citizens and British Overseas Citizens who are re-admissible to the United Kingdom;

• Citizens of British dependent territories who derive their citizenship through birth, descent, registration or naturalization in one of the British dependent territories of Anguilla, Bermuda, British Virgin Islands, Cayman Islands, Falkland Islands, Gibraltar, Hong Kong, Montserrat, Pitcairn, St. Helena or the Turks and Caicos Islands;

• Persons holding passports or travel documents issued by the Holy See.