The Court of Appeal for Ontario (frequently mistakenly referred to as the Ontario Court of Appeal) (ONCA is the abbreviation for its neutral citation) is the appellate court for the province of Ontario, Canada. The seat of the court is Osgoode Hall in downtown Toronto (also the seat of the Law Society of Ontario and the Divisional Court of the Ontario Superior Court of Justice).

The Court is composed of 22 judicial seats, in addition to 10 justices who currently sit supernumerary.^[1] They hear over 1,500 appeals each year, on issues of private law, constitutional law, criminal law, administrative law and other matters. The Supreme Court of Canada hears appeals from less than 3% of the decisions of the Court of Appeal for Ontario, therefore in a practical sense, the Court of Appeal is the last avenue of appeal for most litigants in Ontario.^[2]

Among the Court of Appeal's most notable decisions was the 2003 ruling in Halpern v Canada (AG) that found defining marriage as between one man and one woman to violate Section 15 of the Canadian Charter of Rights and Freedoms, legalizing same-sex marriage in Ontario and making Canada the first jurisdiction in the world where same-sex marriage was legalized by a court ruling. Among many judges from the Court who have been elevated to the Supreme Court of Canada are Justices Rosalie Abella, Louise Arbour, Peter Cory, Louise Charron, Andromache Karakatsanis, Bora Laskin, Michael Moldaver, and Mahmud Jamal, as well as Bertha Wilson, who was the first female justice on both the Court of Appeal for Ontario (1975) and the Supreme Court of Canada (1982).

The Court of Appeal derives its jurisdiction from Ontario's Courts of Justice Act.

Supernumerary Justices

• Courts of Ontario
• Supreme Court of Canada