Unprecedented and rising levels of industrial animal farming are undermining the highest attainable standard of health that is WHO’s mandate. During the 2016 World Health Assembly, Director-General Margaret Chan highlighted climate change, antibiotic resistance, and chronic diseases as “slow-motion disasters.” However, their fundamental link to industrial animal farming has continued to be disregarded. A group of scientists and advocates have written an Open Letter to the new Director General of the World Health Organization that describes industrial animal farming as a serious global health challenge. The letter makes the case that while the consumption of meat and other animal products is part of most cultures, large-scale industrial animal farming has gone beyond satisfying dietary needs and cultural practices. The extent to which we now produce and consume animal products is harming our health.