Cardiff is the capital and largest city of Wales. Cardiff had a population of 362,310 in 2021 and forms a principal area officially known as the City and County of Cardiff. The city is the eleventh largest in the United Kingdom. Located in the southeast of Wales and in the Cardiff Capital Region, Cardiff is the county town of the historic county of Glamorgan and in 1974–1996 of South Glamorgan. It belongs to the Eurocities network of the largest European cities. A small town until the early 19th century, its prominence as a port for coal when mining began in the region helped its expansion. In 1905, it was ranked as a city and in 1955 proclaimed capital of Wales. Cardiff Built-up Area covers a larger area outside the county boundary, including the towns of Dinas Powys and Penarth.

Wales is a country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the east, the Bristol Channel to the south, and the Celtic Sea to the south-west. As of the 2021 census, it had a population of 3,107,494. It has a total area of 21,218 square kilometres (8,192 sq mi) and over 2,700 kilometres (1,680 mi) of coastline. It is largely mountainous with its higher peaks in the north and central areas, including Snowdon, its highest summit. The country lies within the north temperate zone and has a changeable, maritime climate. The capital and largest city is Cardiff.