The Insular Celts were speakers of the Insular Celtic languages in the British Isles and Brittany. The term is mostly used for the Celtic peoples of the isles up until the early Middle Ages, covering the British–Irish Iron Age, Roman Britain and Sub-Roman Britain. They included the Celtic Britons, the Picts, and the Gaels.

Brittany is a peninsula, historical country and cultural area in the north-west of modern France, covering the western part of what was known as Armorica during the period of Roman occupation. It became an independent kingdom and then a duchy before being united with the Kingdom of France in 1532 as a province governed as a separate nation under the crown.