Introduction: Pet food production contributes substantially to global environmental pressures, driven largely by animal-derived ingredients. The current study quantified the environmental impacts of 31 commercially available dry dog foods purchased in the UK, categorised as plant-based, poultry-based, red meat-based (beef and lamb) and veterinary renal diets. Method: Environmental metrics including land use (m2/1000 kcal), greenhouse gas emissions (kg CO2eq/1000 kcal), acidifying emissions (g SO2eq/1000 kcal), eutrophying emissions (g PO4 eq/1000 kcal), and freshwater withdrawal (L/1000 kcal) were estimated using life cycle assessment datasets and adjusted for ingredient composition and energy density. Foods were additionally standardised to 100% moisture-adjusted content, and group differences were evaluated statistically. Results and Discussion: Plant-based diets demonstrated the lowest impacts across all measures. Poultry-based and veterinary diets showed intermediate profiles, while beef- and lamb-based foods exhibited substantially higher impacts. Beef-based diets required 101.12 m2 land and emitted 31.16 kg CO2 eq per 1000 kcal dry food, compared to 2.71 m2 land and 2.79 kg CO2 eq for plant-based. Beef-based foods generated 7.1-fold higher acidifying emissions and 16.4-fold higher eutrophying emissions, compared to plant-based foods. Lamb-based foods were the most freshwater intensive (677.01L/1000kcal), compared to plant-based (246.95L/1000kcal). Whilst moving to a circular food system has the potential to reduce environmental impact, current pet food manufacturing practices compete with human food supply and are not nutritionally necessary for dogs to thrive. These findings highlight a major opportunity to mitigate the environmental footprint of companion animal nutrition through reformulation towards higher inclusion of plant-based ingredients.