The European Commission has given the go-ahead for Mittal, the world's biggest steelmaker, to acquire Luxembourg-based rival Arcelor.
The EU commission said the proposed €25.8 billion (£16 billion) takeover of Arcelor, the largest European steel producer, would be consistent with competition law in European Economic Area (EEA) markets.
But it did say the proposed acquisition would impede competition in the heavy beams industry.
Mittal must divest two Arcelor's steel mills in Germany and Italy and its own mill in Poland for the deal to proceed, the commission said.
The three plants combined account for around ten per cent of the total production capacity for heavy section products in the EEA, a commission statement read.
Arcelor has also revealed plans to buy Russian firm Severstal in an apparent bid to repel Mittal's ambitions.
If the merger between Arcelor and Severstal goes ahead, it would create the world's biggest steelmaker.
EU competition commissioner Neelie Kroes said he was "completely satisfied" that Mittal had met requirements for fair competition.