The iron and steel industry is a major contributor to the overall anthropogenic CO2 emissions worldwide, and therefore a significant driver of climate change. This paper explores the possible options for decarbonising iron and steel production processes, focusing on the use of renewable hydrogen as an alternative to fossil coal. It explains the basic physical and chemical differences between the two alternative processes, their cost structures and potential for further cost reductions, as well as the larger implications and longer-term consequences of switching to hydrogen in this key industrial sector.