Arcelor S.A. was the world's largest steel producer in terms of turnover and the second largest in terms of steel output, with a turnover of €30.2 billion and shipments of 45 million metric tons of steel in 2004. The company was created by a merger of the former companies Aceralia (Spain), Usinor (France) and Arbed (Luxembourg) in 2002.

Arcelor is now part of ArcelorMittal.

Employing 310,000 employees in over 60 countries, it is a major player in all its main markets: automotive, construction, metal processing, primary transformation, household appliances, and packaging, as well as general industry. With total sales of over €30 billion, Arcelor is the world's largest steel manufacturer in terms of turnover. It produces long steel products, flat steel products and inox-steel. In January 2006 Arcelor announced the acquisition of Dofasco, Canada's largest steel producer with an annual output of 4.4 million tons. After an intense bidding war against the German ThyssenKrupp, Arcelor had finally bid 5.6 billion Canadian dollars.