Derby is a city and unitary authority area in Derbyshire, England. It lies on the banks of the River Derwent in the south of Derbyshire, of which it was traditionally the county town. Derby gained city status in 1977, and by the 2011 census its population was 248,700.
Derby was settled by Romans, who established the town of Derventio, later captured by the Saxons, and later still by the Vikings, who made their town of Djúra-bý one of the Five Boroughs of the Danelaw. Initially a market town, Derby grew rapidly in the industrial era. Home to Lombe's Mill, an early British factory, Derby has a claim to be one of the birthplaces of the Industrial Revolution. It contains the southern part of the Derwent Valley Mills World Heritage Site. With the arrival of the railways in the 19th century, Derby became a centre of the British rail industry.
Derby is a centre for advanced transport manufacturing, being home to the world's second largest aero-engine manufacturer: Rolls-Royce. Bombardier Transportation has a production facility at the Derby Litchurch Lane Works while Toyota Manufacturing UK's automobile headquarters is located southwest of the city at Burnaston.