Off-road vehicles (ORVs) can be present in three contexts when off formed roads: cross-country; on often vast, expanding, unplanned, and unregulated trail networks; or on “ecosystem roads” (e.g., shorelines). Several of these contexts have escaped previous review, or received only cursory consideration, despite the voluminous road ecology literature. We argue that most of the ecological disruptions realized by formed roads (this book) have also been demonstrated for ORVs off formed roads, yet key differences also exist. By their very nature, vehicles driven beyond official roads often cause more environmental harm because they can traverse areas originally set aside as high-quality wildlife habitat. Not surprisingly, therefore, the available evidence demonstrates widespread and substantial direct and indirect deleterious effects of ORVs, which have been shown to impact numerous habitats, species, biological communities, and disrupt ecological processes. Their impacts are realized in a diversity of habitats, including alpine and polar tundras, deserts, wetlands, and sweeping subtropical and temperate ocean shores. Despite ORV use that is increasing in numbers and expanding in spatial footprint, management (if any) is often reactionary, piecemeal, and rarely achieves significant reductions in environmental harm. The role of new vehicle technologies (e.g., electric powertrains, advanced terrain responses) is uncertain, with both more and fewer ecological impacts being plausible. Driver behavior and motivations determine the degree to which ORV use is environmentally sensitive or otherwise. Thus, we argue for increased research investment that pairs biological field studies with environmental psychology of ORV users, with a view to achieving management that delivers smaller environmental risk while having better social, cultural, and political acceptance.