Reference Re Secession of Quebec, [1998] 2 SCR 217 is a landmark judgment of the Supreme Court of Canada regarding the legality, under both Canadian and international law, of a unilateral secession of Quebec from Canada.

Both the Quebec government and the Canadian government stated they were pleased with the Supreme Court's opinion, pointing to different sections of the ruling.

Following the election of a majority of Parti Québécois (PQ) Members of the National Assembly (MNAs) in the 1976 Quebec provincial election, the party formed a government and, in 1980, held an independence referendum. The government of the Province of Quebec asked the province's population if it should seek a mandate to negotiate sovereignty for Quebec coupled with the establishment of a new political and economic union with Canada. The referendum resulted in the defeat of the sovereignty option, with 59.6% voting no on sovereignty. The PQ was nevertheless re-elected in 1981, this time promising not to hold a referendum.

In 1982, the federal government petitioned the Parliament of the United Kingdom in London to amend Canada's constitution so that, in the future, all further amendments would take place by means of a process of consent involving only the Parliament of Canada and the legislatures of the provinces. Up until this point, all amendments had taken place by means of Acts of the British Parliament, since the Canadian constitution was, strictly speaking, a simple statute of that Parliament. Colloquially, the switch to a domestic amendment procedure was known as patriation. The particular amending formula adopted in 1982 was opposed by the then-government of Quebec. Other concomitant constitutional changes such as the Canadian Charter of Rights and Freedoms were also opposed by Quebec, based not on rejection of their content (since, in 1975, Quebec had adopted a more complete Quebec Charter of Human Rights and Freedoms) but on the manner of their adoption and lack of amendments specific to Quebec in the package.

Subsequently, two attempts were made at amending the Canadian constitution (the Meech Lake Accord in 1987–1990 and the Charlottetown Accord in 1992) that, it was hoped, would have caused the Quebec legislature to adopt a motion supporting the revised constitution. Following the failure of both of these to pass, there was a widespread sense in the mid-1990s that the Constitution of Canada was not fully legitimate because it had not yet received the formal approval of Quebec.

In 1994, the Parti Québécois was re-elected and announced that it would be initiating a second referendum to take place in 1995. This time, the question was on sovereignty with an optional partnership with Canada. The "no" side won by only a narrow margin. Prior to this referendum, the National Assembly of Quebec had adopted a bill relating to the future of Quebec that laid out a plan if secession was approved in a referendum.

In response to the bill and the referendum result, several legal actions were initiated by opponents to the independence of Quebec questioning the legality of secession. In 1996, Parti Québécois leader Lucien Bouchard announced his government would make plans to hold another referendum when he was confident that the "winning conditions" were there, pointing to the political cost of losing a third referendum. In reaction to Bouchard's stated plans, Prime Minister Jean Chrétien initiated a reference on the legality of a unilateral declaration of independence by a Canadian province.

On September 30, 1996, the Cabinet of Jean Chrétien (i.e., the Governor in Council) approved Order in Council PC 1996–1497 under Section 53 of the Supreme Court Act, referring three questions to the Supreme Court of Canada regarding secession.