The Celtic nations where most Celtic speakers are now concentrated

P-Celtic, according to one schema of categorization, is a node of the Celtic languages incorporating the following language groups:

• Gaulish
  • Lepontic
  • Noric
  • Galatian
• Brythonic
  • Cumbric
  • Pictish
  • Old Welsh
  • Middle Welsh
  • Welsh
  • Southwestern Brythonic
    • Breton
    • Cornish

There are two main competing schemata of categorization of Celtic languages. The older P-Celtic/Q-Celtic hypothesis links Gaulish with Brythonic and links Goidelic as Q-Celtic. The difference between P and Q languages is the treatment of Proto-Celtic *k^w, which became *p in the P-Celtic languages but *k in Goidelic.

The other scheme, defended for example by McCone (1996), links Goidelic and Brythonic together as an Insular Celtic branch.