Sheffield is a city and metropolitan borough in South Yorkshire, England. Historically part of the West Riding of Yorkshire, its name derives from the River Sheaf, which runs through the city. With some of its southern suburbs annexed from Derbyshire, the city has grown from its largely industrial roots to encompass a wider economic base. The population of the City of Sheffield is 563,749 and it is one of the eight largest regional English cities that make up the Core Cities Group. Sheffield is the third largest English district by population. The metropolitan population of Sheffield is 1,569,000.

In the 19th century, Sheffield gained an international reputation for steel production. Many innovations were developed locally, including crucible and stainless steel, fuelling an almost tenfold increase in the population in the Industrial Revolution. Sheffield received its municipal charter in 1843, becoming the City of Sheffield in 1893. International competition in iron and steel caused a decline in these industries in the 1970s and 1980s, coinciding with the collapse of coal mining in the area.

The 21st century has seen extensive redevelopment in Sheffield along with other British cities. Sheffield's gross value added has increased by 60% since 1997, standing at £9.2 billion in 2007. The economy has experienced steady growth averaging around 5% annually, greater than that of the broader region of Yorkshire and the Humber.

The city is in the eastern foothills of the Pennines, and the valleys of the River Don and its four tributaries, the Loxley, the Porter Brook, the Rivelin and the Sheaf. 61% of Sheffield's entire area is green space, and a third of the city lies within the Peak District national park. There are more than 250 parks, woodlands and gardens in the city, with an often quoted estimated 2 million trees, and claims of Sheffield having the highest ratio of trees to people of any city in Europe. Roadside trees however are currently being replaced by the council under a controversial 25 year Private finance initiative scheme which commenced in 2012.

The city has a long sporting heritage, and is home to the world's oldest football club.