Rhaeto-Romance, Rheto-Romance, Rhaeto-Italian, or Rhaetian, is a purported subfamily of the Romance languages that is spoken in south-eastern Switzerland and north-eastern Italy.

By the end of the Roman Empire, there was an unbroken region of distinctive Romance speech here, which was gradually fragmented into secluded areas in the high valleys by the encroachment of German dialects from the north and of Gallo-Italic languages from the south.

Rhaeto-Romance was spoken over a much wider area during Charlemagne's rule, stretching north into the present-day cantons of Glarus and St. Gallen, Walensee in the northwest, and Rüthi and the Alpine Rhine Valley in the northeast.

[5] This language shift was a long, drawn-out process, with larger, central towns adopting German first, while the more peripheral areas around them remained Romansh-speaking longer.

The family is most closely related to its nearest neighbors: French, Franco-Provençal, Occitan, Venetian, Istriot and Lombard.

[6] A number of lexical items are shared with Ibero-Romance due to the similar date of Latinization for both regions, although it can also be explained by means of Bartoli's areal linguistics theory, Ibero-Romance being a peripheral area, as are Balkano-Romance, Southern-Italian and Rhaeto-Romance, whereas Gallo-Romance and Italo-Romance are the central area.

The oldest literary text in the Romansh language is the Chianzun dalla guerra dagl Chiaste da Müs, which details the Musso War.

As Heinrich Bansi, a notable priest in 1897, noted: The biggest obstacle to the moral and economical improvement of these regions is the language of the people.

Despite these efforts, with more and more of the surrounding area speaking German, the Lia Rumantscha created Romansh-speaking daycare schools in the 1940s.

An exception to this decline occurred in the mid 20th century when a devastating earthquake struck the local region.

In the early Middle Ages, the Ladin region came under House of Habsburg and Republic of Venice rule.

Benito Mussolini later pushed forward an Italianization of the region which further dwindled the Ladin language user base.

The Rhaeto-Romance languages can be distinguished into the following varieties:[12] A phylogenetic classification[13] using basic lexicon identifies a primary split between Romansh in Switzerland and Ladin in Italy.

This would correspond to a time depth of about 500 years if the glottochronological replacement rate of 14% per millennium for Romance were trustworthy.

Many place names in Romansh date back before Roman contact stemming from Raetic and Celtic origins.

Most words in Friulian are of the Romance variety due to its Latin roots; however, it still has many place names and flora that trace back to Raetic, Venetic and Celtic origins.