At the UN-level, it has only recently been acknowledged that the welfare of animals is not, but should be, part of the Sustainable Development Agenda. Since then, and more vehemently so since the outbreak of the COVID-19 pandemic, initiatives and publications have come out, drawing out the interconnections between animal welfare and protection on the one hand, and on the other hand, ecosystem destruction, species extinction, the climate crisis, industrial animal agriculture and the emergence of zoonoses. Arguments have also been made that sustainability and animal protection is something of an oxymoron with in particular farm animals being treated as vehicles to achieve sustainability rather than being agents who under a justice perspective should be beneficiaries of the sustainability transition. To address the many un-sustainabilities, many urge to move away from anthropocentric notions of sustainability. Others have begun to approach the notion of sustainability from a critical theory perspective. This parallels developments in relevant related fields. Critical animal studies is already well established. Moreover, we are observing the birth of a new field, the veterinary humanities, with indications of a critical veterinary humanities emerging. In this paper, it is discussed what a critical theory perspective would bring to the intersection of global sustainability and animals. In conclusion, an interspecies sustainability theory is suggested that needs to be conceptualised as a critical theory to address the multiple sustainability crises and to protect animals.