A visitor visa, also referred to as a Temporary Resident Visa (TRV), is an immigration document that allows foreign nationals to travel to and enter Canada. Unless you are from a visa-exempt country, you will need a visitor visa to enter Canada whether you are coming as a student, temporary worker, or simply to visit.
There are two types of Canadian visitor visas: single entry visas and multiple entry visas. A single entry visa allows foreign nationals to enter Canada for one-time only. A multiple entry visa allows holders to enter and leave Canada as often as they want as long as the visa is valid. You don’t need to choose which kind to apply for, applicants are automatically considered for multiple entry visas and are only issued single entry visas under unique circumstances.
Multiple entry visitor visas permit the holder to travel to Canada for six months at a time as many times as they want, as long as the visa remains valid. They can be valid for up to 10 years, but the exact validity period is at the discretion of the visa officer issuing it. If you have some other status document, such as a study permit or a work permit, and are not otherwise visa-exempt, you will automatically be issued a visitor visa allowing you to enter Canada to receive your permit. Usually, this is a multiple entry visa. If you choose to temporarily leave Canada during the course of your studies or temporary work, you will not need to apply for a new visitor visa to re-enter Canada as long as your permit and visa are both still valid.
Everyone who wants to enter Canada who is not a Canadian citizen or permanent resident, or otherwise visa-exempt, requires a visitor visa. Canadian permanent residents are not permitted to apply for a visitor visa, even if their permanent resident card has expired. They must instead apply for a permanent resident travel document (PRTD). Canadian citizens, including dual citizens, are also not permitted to apply for a visitor visa. They must be travelling on a valid Canadian passport. If you are transiting through or coming to Canada for business, not as a temporary foreign worker, you may need a business visitor visa.
The only people, other than Canadian citizens and permanent residents, who do not require a visitor visa to enter Canada are individuals who are visa-exempt. Canada has agreements with several countries that exempt citizens of those nations from requiring a visa to visit Canada for a period of up to six months. If foreign nationals from visa-exempt countries wish to visit Canada by air, they require a valid electronic travel authorization (eTA).
If they choose to visit by land or by sea, they only require their valid passport issued by a visa-exempt country. The only exception is citizens of the United States. The Canada-U.S. border is the longest undefended land border in the world, and thousands of Canadian and U.S. citizens cross that border every day. U.S. citizens are able to travel to Canada on a valid U.S. passport, and do not require a visitor visa or eTA, provided they are not staying for a period longer than six months. U.S. permanent residents, or Green Card holders, are visa-exempt regardless of their country of citizenship. They require an eTA to fly to or transit through a Canadian airport, and must present a valid Green Card and a valid passport to enter Canada.