["Bioethics, EarlyView. ", "\nABSTRACT\nExtreme heat is emerging as one of the most consequential occupational hazards of the 21st century. More than 2.4 billion workers, over 70% of the global labour force, are exposed to excessive heat, with more than 22 million heat‐related occupational injuries and nearly 19,000 deaths each year. By 2030, heat stress is projected to reduce global working hours by 2.2%, equivalent to 80 million full‐time jobs, with the heaviest losses concentrated in low‐ and lower‐middle‐income countries. This paper argues that these figures disclose not only a climate and labour crisis, but also a problem of health justice. To conceptualise this, the article develops the framework of ‘heat debt’ to articulate the physiological, economic, and temporal burdens disproportionately imposed on workers to sustain global production, supply chains, and essential services in a warming world. Synthesising evidence from agriculture, construction, garment manufacturing, informal urban labour, and healthcare, this paper demonstrates that this debt is systematically offloaded onto low‐wage, migrant, informal, and feminised workforces. The analysis proceeds in three parts. First, it argues that excessive occupational heat must be analysed through the lenses of distributive and reparative justice. Second, it demonstrates how current labour law, climate policy, and corporate supply chain governance institutionalise thermal inequality. Third, it interrogates health systems in their dual capacity: as primary responders to heat‐related morbidity, and as occupational environments that actively reproduce heat vulnerability among clinical staff. The article concludes by advancing a bioethical mandate of ‘cooling as care,’ positing that occupational thermal protection is an indispensable prerequisite for climate justice, decent work, and ethically defensible healthcare delivery.\n"]