The mouflon (Ovis gmelini musimon) is an introduced ungulate in continental Europe. It has adapted well to its occupied habitats over the last 150 years. Its growing population has drawn increasing attention to its impact on autochthonous species, especially in endangered ecosystems. Its allochthonous character, habitat selection, and feeding led scientists to question the raison d’etre of mouflons. The mouflon’s space use and foraging strategies highlighted some pressure elements it exerts on those habitats. Mouflon trampling damage may be behind the degradation of rare, endangered grasslands. We review studies to discuss the results and the limitations of exclusion experiments to evaluate the extent of mouflon-caused damage in the context of population density. We review the forest damage attributed to mouflons considering interspecies competition with other large herbivores such as red deer (Cervus elaphus) and chamois (Rupicapra rupicapra). Climate change makes the mouflon use its space differently when seeking shelter in southern habitats; consequently, the increased trampling and foraging pressures suggest new challenges in managing its impact. We review research results on these direct impacts of the species; however, the long-term effects on herbaceous plant communities, such as rock grasslands, are still unclear. This is true for the mouflon’s influence under changing population dynamics. Our results intend to set directions for future research on long-term experiments with density impact, coexistence with red deer or chamois, and warming-climate-driven behavior change.