Switzerland is divided into 23 cantons, three of which are divided into half-cantons.  There are German-speaking and French-speaking cantons, one Italian-speaking canton and cantons in which both German and French are spoken. In one canton (Graubünden) German, Italian and Rumantsch are spoken.

The cantons vary greatly as to size and character. The canton of Geneva is virtually made up of just of one city. Some other cantons, like Uri, consist almost entirely of mountains and valleys. The cantons vary greatly in size and in population density. Basel-Town, with its 37 km2 (14 square miles) has almost as many inhabitants (186,700) as the largest canton, Graubünden, whose 187,800 inhabitants are spread across 7,105 km2 (2,743 square miles) and 150 valleys. The canton of Zurich has over a million inhabitants, while the entire population of some other cantons would merely fill a small football stadium. Appenzell Inner-Rhodes, for example, has a total of 15,100. Not all the cantons are single territorial entities: some have small exclaves completely surrounded by the territory of other cantons.

Some of the cantons have deep historical roots as autonomous entities within Switzerland; others either joined later, or split off from existing cantons. The newest is the canton of Jura, which separated from the canton of Bern in 1979. Three of the cantons consist of two half-cantons.

The composition of Switzerland is not fixed in stone. For example, in 2002 the citizens of Geneva and Vaud were invited to vote on whether their cantons should merge - although they overwhelmingly rejected the move. The half-canton of Basel-Country has spearheaded a movement to make each Basel a full canton, but this is opposed by a majority in the National Assembly because it would upset the federal balance.

There are also some communes which want to change cantons. In a celebrated case in 1996, the whole country was called to vote on whether the village of Vellerat, with a population of 70, should be allowed to leave canton Bern and join canton Jura. Its wish was granted.