Cardiff is the capital and largest city of Wales, with recent local government estimates stating the city's population as being 317,500. Cardiff, part of the Eurocities network of the largest European cities, is administered as a unitary authority, having previously being part of the historic county of Glamorgan (and later South Glamorgan). Cardiff Urban Area covers a slightly larger area, including Dinas Powys, Penarth and Radyr.

Cardiff is home to the Welsh government in Cardiff Bay and much of the media in Wales. Doctor Who and Torchwood along with other series are filmed mostly within the City and County of Cardiff. It has the biggest media sector in the UK outside London, being home to several studios as well as BBC Wales, HTV and S4C. Several radio stations are based in the city such as Red Dragon FM, Xfm, Real Radio, Radio Cymru and Radio Wales. The newspapers Western Mail and South Wales Echo (both owned by Trinity Mirror) are based in Cardiff.

Cardiff was a small town until the early 19th century and came to prominence as a major port for the transport of coal following the arrival of industry in the region. Cardiff was made a city in 1905, and proclaimed capital of Wales in 1955.