Endesa, S.A. (Spanish pronunciation: [enˈdesa], originally an initialism for Empresa Nacional de Electricidad, S.A.) is a Spanish multinational electric utility company, the largest in the country. The firm, a majority-owned subsidiary of the Italian utility company Enel, has 10 million customers in Spain, with domestic annual generation of over 97,600 GWh from nuclear, fossil-fueled, hydroelectric, and renewable resource power plants. Internationally, it serves another 10 million customers and provides over 80,100 GWh annually. Total customers numbered 22.2 million as of December 31, 2004. It also markets energy in Europe. The company has additional interests in Spanish natural gas and telecommunications companies.

Endesa is one of the three large companies in the electricity sector in Spain, which together with Iberdrola and Naturgy, dominate around 90% of the national electricity market. Endesa carries out activities of generation, distribution and commercialization of electricity, natural gas and renewable energythrough Enel Green Power.