Cardiff is the capital, largest city and most populous county of Wales. The city is Wales' chief commercial centre, the base for most national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for Wales. According to recent estimates, the population of the unitary authority area is 324,800, while the wider metropolitan area has a population of nearly 1.1 million, more than a third of the total Welsh population. Cardiff is a significant tourism centre and the most popular visitor destination in Wales with 14.6 million visitors in 2009.

The city of Cardiff is the county town of the historic county of Glamorgan (and later South Glamorgan). Cardiff is part of the Eurocities network of the largest European cities. The Cardiff Urban Area covers a slightly larger area outside of the county boundary, and includes the towns of Dinas Powys, Penarth and Radyr. A small town until the early 19th century, its prominence as a major port for the transport of coal following the arrival of industry in the region contributed to its rise as a major city.