The twenty-six cantons of Switzerland are the states of the federal state of Switzerland. Historically and until the mid-19th century, each canton in the then-confederation was a sovereign state, with its own borders, army, and currency; the current federal structure was established in 1848.

During the sixteenth century, the Swiss Confederation was composed of thirteen self-governed states. These states were called cantons, and there were two different kinds of cantons: the six forest cantons and seven urban cantons. Though they were technically part of the Holy Roman Empire, they had become almost completely independent when the Swiss defeated Emperor Maximillian in 1499.

The six forest cantons were democratic republics, while the seven urban cantons were governed by city councils. However, these city councils were controlled by small oligarchies of wealthy citizens. The urban cantons included Zürich, Bern, and Basel.

Each canton has its own constitution, legislature, government and courts. Most of the cantons' legislatures are unicameral parliaments, their size varying between fifty-eight and two hundred seats. A few legislatures are general assemblies (Landsgemeinden). The cantonal governments consist of either five or seven members, depending on the canton.

All tasks that do not explicitly fall within the Confederation according to the Swiss Constitution are matters of the cantons. The cantons determine the degree of autonomy of the municipalities, thus this varies greatly. The sizes of the cantons are extremely different: from just 37 to 7,105 square km; the populations vary from 14,900 to 1,244,400.

In cantonal matters, direct democracy in the form of general assemblies (Landsgemeinde) is now confined to the cantons of Appenzell Innerrhoden and Glarus. In all other cantons democratic rights are expressed using the ballot box. Since the creation of the Canton of Jura in 1978 there have been no new cantons. According to the constitution of 1999 , the number of cantons is officially twenty-six, but the number of states (Stände) relevant for election of the Council of States (Ständerat) and voting in federal Initiatives, is twenty-three: the cantons of Unterwalden, Appenzell, and Basel are counted as two half-cantons each. Unterwalden is divided into Obwalden and Nidwalden, Appenzell into Innerrhoden and Ausserrhoden, while Basel is divided into Basel-Stadt and Basel-Landschaft.

The table below lists the cantons in the order of the constitution.

The two-letter abbreviations for Swiss cantons are widely used, e.g. on car license plates and in the ISO 3166-2 codes (with the prefix "CH-", i.e. CH-SZ for the canton of Schwyz).