An oil refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, heating oil, kerosene, and liquefied petroleum gas.

OOC has shares in two refinery companies, one in Oman (ORPC) and another in Hungary (MOL). ORPC has two refinery complexes, one in Muscat and another in Sohar. MOL has three refinery complexes one each in Hungary, Slovakia and Italy. OOC also owns shares in two marketing companies in Oman and in UAE, that market the products of its refinery as well as other products.