Enagás, S.A. (Spanish pronunciation: [enaˈɣas], originally an initialism for Empresa Nacional del Gas) is a Spanish energy company and European transmission system operator (TSO), which owns and operates the nation's gas grid. The firm also owns four liquefied natural gas regasification terminals in the country, at Huelva, Barcelona, Cartagena and Gijon. In addition, it owns 50% of the plant BBG (Bilbao) and 72.5% of the Saggas terminal in Sagunto. The chairman of Enagás is Antonio Llardén Carratalá and his chief executive officer is Arturo Gonzalo Aizpiri. The firm's headquarters are located in Madrid. Apart from Spain, Enagás has presence in Mexico, Perú, Chile, Sweden and in the Trans Adriatic Pipeline (TAP) European project.

The company was founded in 1972 by the Spanish Government with the aim of creating a nationwide network of gas pipelines. After privatisation in 1994, Gas Natural acquired a controlling stake in the company. Since Enagás demerged in 2002, Gas Natural gradually decreased its stake to 5%, the maximum allowed for any shareholder by the Government after 30 December 2006. As of 2006, the institutional shareholder was the state-owned holding company Sociedad Estatal de Participaciones Industriales (SEPI) which held 5% of Enagás.

Since 2019, 90% of the company's shares are on the open market (free float).