British Steel was a major British steel producer. It originated from the nationalised British Steel Corporation (BSC), formed in 1967, which was privatised as a public limited company, British Steel plc, in 1988. It was once a constituent of the FTSE 100 Index. The company merged with Koninklijke Hoogovens to form Corus Group in 1999.

The Labour Party came to power at the 1945 general election, pledging to bring several industries into state ownership. In 1946, it put the first steel development plan into practice with the aim of increasing capacity. It passed the Iron and Steel Act 1949, which meant nationalisation of the industry, as the government bought out the shareholders, and created the Iron and Steel Corporation of Great Britain. American Marshall Plan aid in 1948–50 reinforced modernisation efforts and provided funding for them. However, the nationalisation was reversed by the Conservative government after 1952.

The industry was re-nationalised in 1967 under another Labour government, becoming British Steel Corporation (BSC). But by then, 20 years of political manipulation had left companies, such as British Steel, with serious problems: a complacency with existing equipment, plants operating below full capacity (hence the low efficiency), poor-quality assets, outdated technology, government price controls, higher coal and oil costs, lack of funds for capital improvement, and increasing competition on the world market.

By the 1970s, the Labour government's main goal for the declining industry was to keep employment high. Since British Steel was a major employer in depressed regions, it was decided to keep many mills and facilities operating at a loss. In the 1980s, Conservative Prime Minister Margaret Thatcher re-privatised BSC as British Steel. Under private control, the company dramatically cut its workforce and underwent a radical reorganisation and massive capital investment to again become competitive in the world marketplace.

Alasdair M. Blair (1997), Professor of International Relations and Head of the Department of Politics and Public Policy at De Montfort University, has explored the history of British Steel since the Second World War to evaluate the impact of government intervention in a market economy. He suggests that entrepreneurship was lacking in the 1940s; the government could not persuade the industry to upgrade its plants. For generations, the industry had followed a piecemeal growth pattern that proved relatively inefficient in the face of world competition.

BSC was formed from the assets of former private companies which had been nationalised, largely under the Labour government of Harold Wilson, on 28 July 1967. Wilson's was the second attempt at nationalisation; the post-war government of Clement Attlee had created the Iron and Steel Corporation of Great Britain in 1951 taking public ownership of 80 companies but this had been largely reversed by the following Conservative governments of the 1950s with only Britain's largest steel company, Richard Thomas and Baldwins, remaining in public ownership.

BSC was established under the Iron and Steel Act 1967, which vested in the corporation the shares of the fourteen major UK-based steel companies then in operation, being:

At the time of its formation, BSC comprised around ninety per cent of the UK's steelmaking capacity; it had around 268,500 employees and around 200 wholly or partly-owned subsidiaries based in the United Kingdom, Australia, New Zealand, Canada, Africa, South Asia, and South America.