Derby is a city and unitary authority area in the ceremonial county of Derbyshire, England. It lies on the banks of the River Derwent in the south of Derbyshire, of which it was traditionally the county town. In the 2011 census, the population of the city was 248,700, with 1,543,000 in the wider metro area. Derby gained city status in 1977.

Derby was settled by Romans – who established the town of Derventio – Saxons and Vikings, who made Derby 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, home to the world’s second largest aero-engine manufacturer, Rolls-Royce, and Derby Litchurch Lane Works, for many years the UK's only train manufacturer. Toyota Manufacturing UK's automobile headquarters is south west of the city at Burnaston.