The research question addressed in this thesis is whether environmental biosecurity in Australia could be improved by incorporating the ecological integrity concept into biosecurity law and administration. Biosecurity at its simplest is the prevention of harm to living things from other living things. Environmental biosecurity is biosecurity aimed at protecting the natural environment rather than human health and industry. Weeds are one of the most significant environmental biosecurity concerns in Australia, but successive State of the Environment Reports confirm that the problems continue and often increase, with financial, economic and public amenity impacts as well as environmental damage. Because environmental biosecurity has been too long subservient to health and industry biosecurity, a breakthrough is needed even if the industry paradigm persists. The ‘wicked’ problems besetting environmental biosecurity need new connections among the many interests and disciplines involved. The ecological integrity concept is untried in this context and is the focus of this thesis. In this thesis I first outline the history of biosecurity and its management in Australia to demonstrate how and why environmental biosecurity regulation has continued to lag behind that for human health and industry. This is despite recognition of the need to manage environmental biosecurity better in major studies and reviews beginning in the 1990s. I set out influences currently affecting environmental biosecurity, such as continuing global changes to the natural world, and the several factors that are inhibiting improvement with it, based primarily around current economic paradigms, reductionist thinking and adverse action and government decisions on budgets, research and administrative arrangements. I argue that trade and agriculture interests continue to dominate biosecurity management, and, although desirable, there is no sign of a paradigm shift away from that domination. Therefore, any improvement must come from applying new approaches within the current legal and administrative frameworks. I argue that ecological integrity could be the basis of one such approach. At its simplest ecological integrity is about maintaining the quality of an ecosystem in which the ecological processes sustain the function, composition and structure of the system. The concept of ecological integrity has been discussed for the last forty or so years, but there are few examples of its successful application in practical situations. I argue that new state biosecurity regimes in Australia provide an opportunity to explore the possibility and potential benefits of incorporating the ecological integrity concept in their administration. I argue there would be gains from incorporating this concept in biosecurity administration, with potentially greater gains driven by some modest legislative changes. One overall outcome would be a more ecocentric approach to biosecurity administration that is readily translatable to any other legal and administrative regime affecting the environment, such as for natural resource management, nature conservation, planning and adaptation to the consequences of continuing global changes with their attendant disruptions. Another outcome is a basis for transformation of community attitudes towards more ecocentric thinking and action. Yet another is providing practical foundations for various proposals aimed at substantial law reforms favouring ecological sustainability and explicit recognition of the rights of nature. There are some challenges that need to be met to maximise value from applying the ecological integrity concept. Without the proposed changes, however, the current deterioration in environmental biosecurity will continue, and probably accelerate because of global changes. The overall environmental biosecurity problems will remain more ’wicked’ than they need to be.