The iron and steel sector accounts for almost 8% of global emissions, making it one of the highest emitting industry sectors with around 30% of industrial carbon emissions. Decarbonising the steel sector is therefore key to achieving climate goals. This report, prepared for the 2023 Japanese G7 Presidency, demonstrates that considering the heterogeneity of steel industries is vital for reaching climate goals and for a just and inclusive transition to a low-carbon future. The report maps the heterogeneity of global steel industries, highlighting the differences between them in key areas relevant to decarbonisation. Additionally, it examines how these differences should be considered when developing definitions for near-zero and low-emissions steel production, as well as emissions measurement methodologies and data collection frameworks.