Terrorism and mass attacks in Canada includes acts of terrorism, as well as mass shootings, vehicle-ramming attacks, mass stabbings, and other such acts committed in Canada that people may associate with terroristic tactics but have not been classified as terrorism by the Canadian legal system. (For example, the 2018 Toronto shooting was a mass shooting that law enforcement officials did not connect to terrorism.)

The Criminal Code of Canada defines terrorist activity to include an "act or omission undertaken, in or outside Canada, for a political, religious or ideological purpose, that is intended to intimidate the public with regard to its security, including its economic security, or to compel a person, government or organization (whether in or outside Canada) to do or refrain from doing any act, and that intentionally causes one of a number of specific forms of serious harm." As such, some of the terrorist acts listed here are related to external events and nationalities, while others, such as the FLQ crisis in 1970, are related to internal tensions within the country.

Matters relevant to overall counterterrorism in Canada, as well as national security within the federal government, fall under the jurisdiction of the Minister of Public Safety and Emergency Preparedness, who heads Public Safety Canada (PSC). Two other ministers with particularly crucial roles with respect to counter-terrorism are the Ministers of Foreign Affairs and of National Defence.

The Canadian government uses the National Terrorism Threat Level (NTTL) to identify the probability of terrorism occurring in Canada. As of 22 May 2021^[update], Canada's current threat level is "Medium," which means that a "violent act of terrorism could occur;" it has been at this level since October 2014.

Overall issues of national security fall under the jurisdiction of the Minister of Public Safety and Emergency Preparedness, who heads Public Safety Canada (PSC). While provincial and territorial governments are responsible for general law enforcement and criminal prosecutions, the Royal Canadian Mounted Police (part of the PSC portfolio) is given primary responsibility, under the Security Offences Act (SOA), for the investigation of offences involving national security.

Canadian federal statutes establish a legal regime that prosecutes terrorists for their activities. The Public Prosecution Service of Canada (PPSC), under the Attorney General of Canada, prosecutes offenses on behalf of the Canadian government, including those involving national security such as terrorist activities. If a person carries out a terrorist attack or instructs someone else to carry out a terrorist attack, they are given a life sentence. Anyone who facilitates a terrorist attack is liable to imprisonment for no more than 10 years.

The Criminal Code defines terrorist activity to include an "act or omission undertaken, in or outside Canada, for a political, religious or ideological purpose, that is intended to intimidate the public with regard to its security, including its economic security, or to compel a person, government or organization (whether in or outside Canada) to do or refrain from doing any act, and that intentionally causes one of a number of specific forms of serious harm."

The Combating Terrorism Act, which came into force in July 2013, renewed parts of the Criminal Code by creating four new offences intended to prevent and deter individuals from leaving Canada for particular terrorism-related purposes.