After providing some background about the importance of cotton as a fibre, this article provides information about the global relevance of China’s and Australia’s cotton industries and compares the structure and other significant features of their cotton industries. Attention is given to trends in overall cotton yields and the volume of production of cotton globally, in Australia, and in China as indicators of the sustainability of cotton supplies. Some simple economic theory is applied to indicate the relationship between market conditions and the sustainability of global cotton supplies. Then the environmental and economic factors that challenge the sustainability of Australian cotton production are outlined and analysed and this is done subsequently for China’s cotton production. Geographical and regional features that affect the sustainability of cotton supplies in Australia and China are given particular attention. Some new economic theory is proposed to model hysteresis in Australia’s supplies of cotton. Ways of coping with the sustainability difficulties that are being encountered by both these nations are compared. Many of the sustainability challenges facing these two countries are found to differ but some of their environmental obstacles to sustainable cotton production are similar.