The Bethlehem Steel Corporation was an American steelmaking company headquartered in Bethlehem, Pennsylvania. Until its closure in 2003, it was one of the world's largest steel-producing and shipbuilding companies. At the height of its success and productivity, the company was a symbol of American manufacturing leadership in the world, and its decline and ultimate liquidation in the late 20th century is similarly cited as an example of America's diminished manufacturing leadership. From its founding in 1857 through its 2003 dissolution, Bethlehem Steel's headquarters were based in Bethlehem, Pennsylvania, in the Lehigh Valley region of the United States. Its primary steel mill manufacturing facilities were first located in Bethlehem, Pennsylvania and later expanded to include a major research laboratory in Bethlehem, Pennsylvania, and plants in Sparrows Point, Maryland, Johnstown, Pennsylvania, Lackawanna, New York, and its final and largest site in Burns Harbor, Indiana.

Steelmaking is the process of producing steel from iron ore and/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium, carbon and vanadium are added to produce different grades of steel.