In historical linguistics, Italo-Celtic refers to the observation that the Italic languages and the Celtic languages share a number of common features unique to these two groups.

The traditional interpretation of the data is that these two subgroups of the Indo European language family are generally more closely related to each other than to the other Indo European languages. This is usually taken to imply that they are descended from a common ancestor, a phylogenetic Proto-Italo-Celtic which can be partly reconstructed by the comparative method.

The Italo-Celtic Verb

Based on features of Italic and Celtic languages, the following kind of endings have been reconstructed for Italo-Celtic:

Secondary active Transitive middle Passive Intransitive middle
Sg.1 -m -ma -a, -ōro
Sg.2 -s -sto -to, -toro
Sg.3 -t -to -toro -o, -oro, -tro
Pl.1 -mo -mosdha -modha, -moro
Pl.2 -te -sdhue -dhue
Pl.3 -nt -nto -ntoro -ntro