Centum is the collective name for the branches of Indo-European in which the so-called Satem shift, the change of palato-velar *k^{^}, *g^{^}, *g^{^h} into fricatives or affricates, did not take place, and the palato-velar consonants merged with plain velars (*k, *g, *g^h). Most of the Centum languages preserve Proto-Indo-European labio-velars (*k^w, *g^w, *g^wh) or their historical reflexes as distinct from plain velars; for example, PIE *k, *k^w > Latin c /k/, qu /k^w/, Greek /k/, /p/ (or /t/ before front vowels), Gothic /h/, /h^w/, etc.

The name Centum comes from the Latin word centum '100', pronounced [kentum] < PIE *k^{^}mtom, illustrating the falling together of *k and *k^{^}. Compare Sanskrit s′ata- or Russian sto, in which *k^{^} changed into a fricative.

The Centum branches include Anatolian, Tocharian, Italic, Celtic, Germanic, Greek, and a number of minor and little known extinct groups (such as Venetic and the ancient Macedonian language and probably the Illyrian languages).

The Centum group is a paraphyletic group and thus not a phylogenetic unit.