The term sovereigntist (also spelled sovereignist), or souverainiste in French, refers to proponents of two distinct political ideologies, depending on the society.

• In Quebec, a sovereigntist is an advocate of the Quebec sovereignty movement that calls for an independent Quebec. The term derives from the neologism souverainisme that René Lévesque initiated to qualify the movement, notably with the manifest Option Québec and the founding of the Mouvement Souveraineté-Association, the direct predecessor of the Parti Québécois.

• In France, a sovereigntist is a eurosceptic proponent of retrieving the French Republic from the European Union.

While the two deal with the concept of political sovereignty, they actually differ on mainly one aspect. Most Quebec sovereigntists are not opposed to the idea of relatively decentralized supranational unions of a confederal nature, where partner nations are considered equal, quite on the contrary.

The main current party with the Quebec sovereignty ideal, the Parti Québécois, actually has a long history of basing itself on the European Union to sketch its plan for a similar union between eventual sovereign, equal coutries of Quebec and Canada. Many renown Quebec sovereigntists are admirerers of the European Union, like current PQ leader Bernard Landry. René Lévesque himself spoke of independence within interdependence and slightly preferred the word souverainiste to indépendantiste because, in his opinion, it highlighted this dichotomy.