Celts, normally pronounced /kɛlts/ (see article on pronunciation), now refers primarily to the members of any of a number of peoples in Europe using the Celtic languages, which form a branch of the Indo-European languages. It can refer in a wider sense to those who participate in a Celtic culture. However, in ancient times, the term 'celts' was used either to refer generally to barbarians in north-western Europe or to specific groups of tribes in the Iberian Peninsula and Gaul. The focus of this article is the ancient Celtic peoples of Europe; for the Celts of the present day, see Modern Celts.
Although once restricted to the Atlantic coast of Western Europe, the so-called "Celtic fringe", Celtic languages were once predominant over much of Europe, from Ireland and the Iberian Peninsula in the west to northern Italy and Serbia in the east. Archaeological and historical sources show that at their maximum extent in the third century BC, Celtic peoples were also present in areas of Eastern Europe and Asia Minor.citation needed]