The ecological footprint is studied as a macroindicator of sustainability applicable to companies and corporations. Until now, this macroindicator has been applied to cities, regions, or countries. It accounts for the consumption of natural resources by converting them into hectares of “nature” or consumed productive land. The parameters analyzed in this research have been consumption of energy, fuel, material, paper, wood, water, built land, and green areas, and residues generated by the Gijón Port Authority, Spain. The results show a net ecological footprint of 3,279.84 ha. The main components of the footprint are construction works (nearly 2,000 ha) and electricity consumption (679 ha). Studies of this kind enable companies to design sustainable development plans to reduce consumption as well as develop “green” (footprint-free) products and create “natural capital” (wastage absorption). Until now, these issues have not been on the agenda of companies, but they are indispensable in achieving real sustainability.