Pilbara Iron is a wholly owned subsidiary of the multinational Rio Tinto Group, that manages assets for Hamersley Iron Pty Ltd, a wholly owned subsidiary of Rio Tinto, and Robe River Iron Associates, an unincorporated joint venture between Rio (53% and operator since 2000) and three Japanese steel companies Mitsui Iron Ore Development P/L (33%), Nippon Steel Australia P/L (10.5%) and Sumitomo Metal Australia P/L (3.5%).All of these companies are involved in the mining of iron ore, predominantly from the Pilbara region of Western Australia.
In 2004, Rio Tinto announced that Robe and Hamersley would start merging operations under the new Pilbara Iron entity. The concept had been tested by the formation of Pilbara Rail in 2001, which generated more than $16 million in savings. Pilbara Rail was folded into Pilbara Iron in 2005. Each company continues to market products separately and retains ownership and profits from the underlying mines, as well as strategic development of their own mineral resources.