Campbell is a Scottish and Irish surname —derived from the Gaelic roots cam ("crooked") and beul ("mouth")—that had originated as a nickname meaning "crooked mouth" or "wry mouthed." Clan Campbell, historically one of the largest and most powerful of the Highland clans, traces its origins to the ancient Britons of Strathclyde. Between 1200 and 1500 the Campbells emerged as one of the most powerful families in Scotland, dominant in Argyll and capable of wielding a wider influence and authority from Edinburgh to the Hebrides and western Highlands.

Today, the name is found throughout the world as a consequence of large scale emigration from Scotland from the 18th century onwards and the settlement of the Scottish diaspora in many countries particularly the United States, Canada and Australia. Due to significant Scottish immigration in the 16th and 17th centuries, the name is also found across the island of Ireland but particularly in Ulster. Outside of Ulster, Irish occurrences of the name can also derive from the surname Mac Cathmhaoil, from which also descend the surnames MacCawill, McCaul, MacCall, and Caulfield. The Irish pronunciation of Cathmhaoil ("battle chief") coincided with the Scottish pronunciation of Campbell, and the name was anglicised accordingly.

Campbell is the third most common surname in Northern Ireland, fourth most common in Jamaica, seventh most common in Scotland, 12th most common in Canada, 18th most common in Australia, 41st most common in the United States and 65th most common in England.