Romandy (French: Romandie or Suisse romande; Arpitan: Romandia) is the French-speaking historical and cultural region of Switzerland. In 2020, about 2 million people, or 22.8% of the Swiss population, lived in Romandy. The majority of the romand population lives in the western part of the country, especially the Arc Lémanique region along Lake Geneva, connecting Geneva, Vaud, and the Lower Valais.

French is the sole official language in four Swiss cantons: Geneva, Vaud, Neuchâtel, and Jura. Additionally, French and German have co-official status in three cantons: Fribourg/Freiburg, Valais/Wallis, and Berne/Bern.

The adjective romand (feminine romande) is a regional dialectal variant of roman (modern French romain, i.e. "Roman"); in Old French used as a term for the Gallo-Romance vernaculars. Use of the adjective romand (with its unetymological final -d) in reference to the Franco-Provençal dialects can be traced to the 15th century; it is recorded, as rommant, in a document written in Fribourg in 1424 and becomes current in the 17th and 18th centuries in Vaud and Fribourg; it was adopted in Geneva in the 19th century, but its usage never spread outside of what is now French-speaking Switzerland.

The term Suisse romande has become widely used since World War I; before World War I and during the 19th century, the term Suisse française "French Switzerland" was used, reflecting the cultural and political prestige of France (the canton of Vaud having been created by Napoleon out of former Bernese subject territories, while Geneva, Valais and Jura were even briefly joined to France, as the Léman, Simplon and Mont-Terrible départements, respectively). Suisse romande is used in contrast to Suisse alémanique ("Alemannic Switzerland") the term for Alemannic German speaking Switzerland. Formed by analogy is Suisse italienne ("Italian Switzerland"), which is composed of Ticino and of a part of Grisons.

In Swiss German, French-speaking Switzerland is known as Welschland or Welschschweiz, and the French-speaking Swiss as Welsche, using the old Germanic term for non-Germanic speakers also used in English of Welsh (see *Walhaz). The terms Welschland and Welschschweiz are also used in written Swiss Standard German but in more formal contexts they are sometimes exchanged for französischsprachige Schweiz ("French-speaking Switzerland") or französische Schweiz ("French Switzerland"). Simple Westschweiz "western Switzerland" may also be used as a loose synonym.

"Romandy" is not an official territorial division of Switzerland any more than there is a clear linguistic boundary. For instance, substantial parts of the canton of Fribourg and the western canton of Bern are traditionally bilingual, most prominently in Seeland around the lakes of Morat, Neuchâtel and Bienne (Biel). French is the sole official language in four Swiss cantons: Geneva, Vaud, Neuchâtel, and Jura; and the co-official language – along with German – in the cantons of Valais, Bern, and Fribourg, French speakers forming the majority of the population in the regions of Lower Valais, Bernese Jura and Fribourg francophone ("French-speaking Fribourg"). Bernese Jura is an administrative division of the Canton of Bern, whereas the two others are informal denominations.

The linguistic boundary between French and German is known as Röstigraben (lit. "rösti ditch", adopted in Swiss French as barrière de rösti). The term is humorous in origin and refers both to the geographic division and to perceived cultural differences between the Romandy and the German-speaking Swiss majority. The term can be traced to the WWI period, but it entered mainstream usage in the 1970s in the context of the Jurassic separatism virulent at the time.

The linguistic boundary cuts across Switzerland north-to-south, forming the eastern boundary of the canton of Jura and then encompassing the Bernese Jura, where the boundary frays to include a number of bilingual communities, the largest of which is Biel/Bienne. It then follows the border between Neuchâtel and Bern and turns south towards Morat, again traversing an areal of traditional bilinguism including the communities of Morat and Fribourg. It divides the canton of Fribourg into a western French-speaking majority and an eastern German-speaking minority and then follows the eastern boundary of Vaud with the upper Saane/Sarine valley of the Bernese Oberland. Cutting across the High Alps at Les Diablerets, the boundary then separates the French-speaking Lower Valais from the Alemannic-speaking Upper Valais beyond Sierre. It then cuts southwards into the High Alps again, separating the Val d'Anniviers from the Mattertal.