Spanish politician and diplomatic. Minister of Foreign Affairs.

Son of Enrique de Areilza, doctor of the mining area of Vizcaya, he studied at the Engineering School of Bilbao and became an industrial technical engineer.

In 1932 he married Mercedes Churruca, the countess of Motrico, daughter of José Churruca and granddaughter of Evaristo Churruca (engineer).

He was the president of the Fundación de Estudios para la Política Exterior since its creation. He was a member of the Monarchist Union of Vizcaya, and he ran for Congress in 1934. He was a monarchic candidate for Vizcaya in the legislative elections of 1932 and 1936, however, he was not elected.

When the Spanish Civil War started, he went from Vitoria to Burgos and then to San Sebastián, and finally to Bilbao, when it was occupied by the rebels on 19 June 1937. He was elected major on 21st June 1937 and he held that position until 24th February 1938. He was National Councillor of the Falange and a member of its Political Board (1939).

In 1947 he was placed as a resident to Argentina to carry out the protocol Franco-Perón whereby the credits that resolved the national supply were obtained. After that, he worked at the Spanish Embassy in the United States. During the 1960s, he began to have some political discrepancies regarding Francoism.

He was a member of the private Council of Juan de Borbón /1966-1969), he maintained his position as his general executive secretary until Juan Carlos was designated successor of Franco. He was the Foreign Affairs Minister in the first government of the Monarchy in 1975. On 11th May 1981, he was elected president of the Parliamentary Assembly of the Council of Europe.

In 1987 he was elected member of the Real Academia Española (RAE). He published more than 3,000 press articles and diverse monographies and memories and he won the Premio Espasa de Ensayo for La Europa que queremos in 1986.

In 1992, he published his memories entitled A lo largo del siglo, 1909-1991. He wrote other works such as: Embajadores sobre España, Madrid, Instituto de Estudios Políticos, 1947; Escritos políticos, Madrid, Guadiana, 1968; Cien artículos, Madrid, Revista de Occidente, 1971; Así los he visto, Barcelona, Planeta, 1974; Diario de un ministro de la monarquía, Barcelona, Planeta, 1977; Una Europa en cambio, San Sebastián, Caja de Ahorros Provincial de Guipúzcoa, 1982; Cuadernos de la transición, Barcelona, Planeta, 1983; Memorias exteriores: 1947-1964, Barcelona, Planeta, 1984; Crónica de libertad: 1965-1975, Barcelona, Planeta, 1985; La Europa que queremos, Madrid, Espasa-Calpe, 1986; Luis XIV, el Rey Sol, Barcelona, Planeta, 1990; A lo largo del siglo, 1909- 1991, Barcelona, Planeta, 1993; Tres batallas por Bilbao y otras páginas, Bilbao, Tilo, 1997; Recuerdos de Portugalete, Portugalete, Fundación El Abra, 1998.

Investigó en el Archivo Histórico Nacional (AHN) de Madrid entre 1942 y 1943 consultando la doucmentación de las Secciones de Órdenes Militares y Consejos.