ItaloCeltic

Italo-Celtic is the proposed genetic grouping within the Indo-European language family that would unite the Italic and Celtic branches under a single common ancestor, Proto-Italo-Celtic, before the split into Proto-Italic and Proto-Celtic. The hypothesis emerged in the 19th century; it posits that Italic and Celtic languages share a set of innovations distinguishing them from other branches of Indo-European.

The hypothesis has been influential in historical linguistics, suggesting that Italic and Celtic languages retain closer affinities to each other than to other Indo-European groups. Early proponents associated with this view include August Schleicher, with later advocates such as Karl Brugmann and Antoine Meillet arguing for a close relationship based on phonological and morphological similarities.

Critics note that many alleged correspondences can be explained by areal contact, diffusion in Iron Age Europe, or chance resemblance, and that the data do not consistently support a decisive split from other branches. Some modern scholars treat Italo-Celtic as a hypothesis with limited or disputed evidence, sometimes acknowledging a weaker form of linkage or a shared substrate.

Evidence cited in support includes regular phonological and morphological correspondences and some shared innovations in core lexicon, though these points are contested and not uniformly agreed upon. The consensus today tends to be cautious, recognizing some affinities but not a firmly established Italo-Celtic clade; the issue remains part of broader discussions about the early diversification of the Indo-European languages.

Languages typically discussed in the Italic grouping include Latin, Oscan, and Umbrian, while Celtic encompasses Gaulish, Celtiberian, and the Brittonic and Goidelic branches.