); Romansh: Constituziun federala da la Confederaziun svizraⓘ)[3] of 18 April 1999 (SR 101)[4] is the third and current federal constitution of Switzerland.

The document contains a catalogue of individual and popular rights (including the right to call for popular referendums on federal laws and constitutional amendments), delineates the responsibilities of the cantons and the Confederation and establishes the federal authorities of government.

The Helvetic Republic of 1798–1803 had a constitution largely drawn up by Peter Ochs, in 1803 replaced by the Act of Mediation, which was in turn replaced by the Federal Treaty of 1815, which restored the Confederacy, while the individual cantons drew up cantonal constitutions, in most respects based on the Ancien Régime of the 18th century, but with notable liberal innovations in the constitutions of the new cantons of St. Gallen, Aargau, Thurgau, Ticino, Vaud and Geneva.

[5] Following the French July Revolution in 1830, a number of large assemblies were held calling for new cantonal constitutions.

As a result of the Sonderbund War, Switzerland was transformed into a federal state, with a constitution promulgated on 12 September 1848.

It is a mandate to the State authorities by the Swiss people and cantons, as the Confederation's constituent powers, to adhere to the values listed in the preamble, which include "liberty and democracy, independence and peace in solidarity and openness towards the world".

The latter provision about the "openness" present a drastic contrast with the previous Swiss constitutions which were mostly oriented toward the internal isolationism.

The general provisions contained in Title 1 (articles 1–6) define the characteristic traits of the Swiss state on all of its three levels of authority: federal, cantonal and municipal.

Title 2 also covers the essential rules on the acquisition of Swiss citizenship and of the exercise of political rights.

The second chapter declares the federal power about areas that require uniform regulation, such as relations with foreign states, security, national and civil defence, general aspects about education, research, culture, the aspects about environment and spatial planning, public construction works and transport, energy and communications, economy in general, concerns about housing, employment, social security and health, about the rights of residence and settlement of foreign nationals, and finally about the responsibility regarding the civil and criminal law, weights and measures.