The Celts were an ancient population that dominated northern and western Europe prior to the Roman Empire. The Celtic people consisted of a conglomeration of independent tribes that were culturally connected. Defining the Celts is problematic as the various sources--archaeological, linguistic, and historical—do not always agree. Taken together, the evidence reveals a sophisticated culture that had its origins in the 14th century BCE, transformed remarkably over the next several millennia, and arguably survives even today among speakers of Celtic languages. At their height, around 300 BCE, the Celts inhabited lands from Ireland to Turkey, engaged in long-distance trade with the Mediterranean world, and had already demonstrated the battle prowess that would awe and terrify classical writers down to the Roman invasions of Britain.