The Gallo-Romance branch of the Romance languages includes in the narrowest sense the langues d'oïl and Franco-Provençal. However, other definitions are far broader and variously encompass the Occitan or Occitano-Romance, Gallo-Italic or Rhaeto-Romance languages.

Old Gallo-Romance was one of the two languages in which the Oaths of Strasbourg were written in 842 AD.

The Gallo-Romance group includes:

Other language families often included in Gallo-Romance:

In the view of some linguists (Pierre Bec, Andreas Schorta, Heinrich Schmid, Geoffrey Hull), Rhaeto-Romance and Gallo-Italic form a single linguistic unity named "Rhaeto-Cisalpine" or "Padanian", which includes also the Venetian and Istriot languages, whose Italianate features are deemed to be superficial and secondary in nature.

How far the Gallo-Romance languages spread varies a great deal depending on which languages are included in the group. Those included in its narrowest definition (the langues d'oïl and Arpitan) were historically spoken in the northern half of France, including parts of Flanders, Alsace and part of Lorraine; the Wallonia region of Belgium; the Channel Islands; parts of Switzerland; and Northern Italy.

Today, a single Gallo-Romance language (French) dominates much of the geographic region (including the formerly-non-Romance areas of France) and has also spread overseas.

At its broadest, the area also encompasses Southern France; Catalonia, the Valencian Community, and the Balearic islands in eastern Spain; Andorra; and much of Northern Italy. The historical border between the Northern and Southern varieties of Gallo-Romance languages has been called the Von Wartburg line.