Exotic species are introduced as a result of human travel and trade. That is, directly or not, they are intricately linked to the choices we make as consumers. A fraction of introduced species become invasive and this represents an increasing threat to natural ecosystems, the economy and to society. Protecting and alleviating natural and managed ecosystems from the pressures imposed by exotic invasive species is only possible through knowledge about why certain invaders are indeed detrimental and need to be controlled. Given the sheer dimension in terms of number of native species affected and area invaded, public participation through involvement in monitoring and control activities is crucial to counteract the problem. To this effect, it is important to know exactly what to look for and what tools are available to monitor and control exotic invaders. This is the first comprehensive guidebook for terrestrial exotic invasive species in Ontario, Canada. It focuses on the biology, ecology and management of species that invade hardwood forests, which are major natural resource in Canada. The forestry sector accounts for billions of dollars annually and many thousands of jobs. The book is divided in two main sections. The first provides an introduction to the importance of hardwood forests in Ontario as well as an overview about management practices. The second section focuses on invasive species accounts for fourteen plants, five insects and six pathogens. These species were selected based on science-based criteria stemming from their economic, environmental and societal effects. The book is aimed at a broad audience, including academics, students, natural resource managers, woodlot owners and the general public.