In Canadian law, a reference question or reference case (formally called abstract review) is a submission by the federal or a provincial government to the courts asking for an advisory opinion on a major legal issue. Typically the question concerns the constitutionality of legislation.

The Constitution Act, 1867, gives the federal Parliament the power to create a "General Court of Appeal for Canada", but does not define the jurisdiction of the Court. When Parliament created the Supreme Court of Canada in 1875, it gave the federal Cabinet the power to refer questions to the Supreme Court for the Court's opinion. That provision has been carried forward and is now found in the current Supreme Court Act.

Under that provision, the federal Cabinet may submit a question to the Supreme Court of Canada by means of an order-in-council. Once the questions have been submitted to the Court, the Court has complete control over the process to be followed. The reference is treated in the same way as an appeal. The Attorney General of Canada is entitled to appear before the Court and to make submissions. The Attorneys General of the provinces and territories are entitled to notice of a reference and may appear on it. Interested parties are able to apply for intervener status to make submissions during the hearing. When necessary, the Court may appoint an amicus curiae to submit a factum to support a particular view.

Once the parties have been determined, the Court sets out a timetable for the filing of written submissions, and for the date of the hearing. Parties to the reference file detailed written submissions on the legal issues raised by the reference, supplemented by factual records if necessary. After all written submissions have been filed, the Court holds an oral hearing on the reference questions. At the conclusion of the hearing, the Court typically reserves its decision. At a later date, the Court releases its opinion on the reference, in the form of a detailed written judgment. Individual judges of the Court are entitled to dissent from the majority opinion, in the same way as with judgments in appeals.

The opinion given by the Supreme Court is in the form of a judicial decision but is not legally binding; nevertheless, no government has ever ignored the opinion.

Prior to 1949, there was an appeal from the Supreme Court to the Judicial Committee of the Privy Council of the United Kingdom, sitting in London. The Judicial Committee served as the highest court for the British Empire and Commonwealth. Many federal reference questions were appealed to the Judicial Committee, which had the final say and could overrule the decision of the Supreme Court.

The provincial governments, under their respective Constitutional Questions Acts, are able to submit questions to the provincial Superior Court or Court of Appeal. The process is very similar to the federal government reference questions. Once the provincial Court of Appeal has given its decision on the reference question, the government or other parties to the reference have the right under the Supreme Court Act to appeal the decision to the Supreme Court of Canada.

The jurisdiction of the Supreme Court of Canada to hear an appeal from a provincial reference question was provided in 1922 amendments to the Supreme Court Act.