Canada welcomes more than 35 million temporary residents (non-immigrants) each year. Except for Canadian citizens and permanent residents, all other individuals require permission to enter Canada as a visitor and require either a Temporary Resident Visa (TRV) or an ETA (electronic Travel Authorization), unless they are US Citizens.
Citizens of visa-exempt countries intending to travel to Canada by air are expected to have applied for an obtained an electronic Travel Authorization (ETA) before their departure to Canada.
Exception: Citizens of the United States do not require a TRV or an ETA, but Green Card holders in the United States, require an ETA to come to Canada, regardless of their nationality.
If you are NOT a citizen from a visa-exempt country, you WILL need a TRV to enter Canada.
As of March 15, 2016, travellers with passports from countries that are visa-exempt who enter Canada by air will need an ETA.
The authorization is electronically linked to your passport and is valid for five years or until your passport expires, whichever comes first.
The TRV is a document issued by a Canadian Immigration Visa Office outside Canada, showing that the holder has satisfied the requirements for admission to Canada as a visitor. TRVs may be for single entry or multiple entry. As a general rule, tourists are admitted for a period of six months. Temporary foreign workers and international students are admitted for varying periods of time, as determined on a case-by-case basis. Extensions may be applied for from within Canada.
It is important to note that possession of a valid TRV does not necessarily mean that the Officer at the Canadian Port of Entry will admit the visitor into Canada. At the Port of Entry, all visitors must demonstrate that the purpose of their visit to Canada is of a temporary nature. Officers at the Port of Entry will deny admission to all persons who, in their opinion, do not intend to leave Canada at the expiry of their visitor status.