The Canadian Environmental Protection Act, 1999 (CEPA, 1999; French: Loi canadienne sur la protection de l'environnement (1999)) is an act of the 36th Parliament of Canada, whose goal is to contribute to sustainable development through pollution prevention and to protect the environment, human life and health from the risks associated with toxic substances. It covers a diversity of activities that can affect human health and the environment, and acts to address any pollution issues not covered by other federal laws. As such, the act is a "catch all" piece of legislation that ensures potentially toxic substances are not inadvertently exempt from federal oversight as a result of unforeseen legislative loopholes.

The act also recognizes the contribution of pollution prevention and the management and control of toxic substances and hazardous waste to reducing threats to Canada's ecosystems and biological diversity.

It acknowledges, for the first time, the need to virtually eliminate the most persistent toxic substances that remain in the environment for extended periods of time before breaking down and bioaccumulative toxic substances that accumulate within living organisms.

Two federal ministries, Health Canada and Environment and Climate Change Canada as they were known in 2022, work in partnership to assess potentially toxic substances and to develop regulations to control toxic substances.

Section 93 of the act provides the authority to the federal government to make regulations to restrict and manage the Canadian List of Toxic Substances (LOTS). Toxic substances have characteristics outlined in Section 64. Once a regulation is proposed, interested parties have 60 days to provide comments on the proposed instrument or may file a notice of objection requesting that a board of review be established.

The act was originally enacted in 1988 and was designed to provide a systematic approach to assess and manage chemical substances in the environment that were not addressed under existing programs.^{[citation needed]}

In 1990 with SOR/90-583: Ozone-depleting Substances Regulations No. 2 (certain bromofluorocarbons) were added to the LOTS.

In 1997 the Supreme Court of Canada adjudicated the case of R. v. Hydro-Québec, by which an attempt was made to enforce the CEPA in the matter of poly-chlorinated biphenyls as a large quantity of said substances had been dumped into a stream by the respondent. Justices Gérard La Forest, Claire L'Heureux-Dubé, Charles Gonthier, Peter Cory and Beverley McLachlin held that "the environment is not, as such, a subject matter of legislation under the Constitution Act, 1867. Rather, it is a diffuse subject that cuts across many different areas of constitutional responsibility, some federal, some provincial. If a provision relating to the environment in pith and substance falls within the parameters of any power assigned to the body that enacted the legislation, then it is constitutionally valid." The fines were upheld and the CEPA was deemed valid legislation under the criminal law power.