César Alierta Izuel (5 May 1945 – 10 January 2024) was a Spanish businessman, who was the chief executive officer and chairman of Telefónica S.A. from 26 July 2000, until replaced by José María Álvarez-Pallete in 2016.

In April 2008, he was named president of the Social Council of the Universidad Nacional de Educación a Distancia (UNED),[2] Spanish main open university, with over 100,000 students.

[6] (source:EFE) In June 2010, the President of Telefónica was rated as the best chief executive officer (CEO) of Spain by Thomson Extel Survey 2010.

[8] On 28 September 2010, he joined the Board of the company resulting from the merger between Iberia and British Airways, International Airlines Consolidate Group (IAG).

[9] In June 2012 the German Chamber of Commerce for Spain awarded César Alierta the Hispanic-German Prize to Business Excellence, for having succeeded in placing the company among the world's telecommunication industry leaders, with a very prominent presence in Germany through O2, a subsidiary of Telefonica.

Textual declarations include: "we do everything and they (developers, content providers, search engines...) only have the algorithms", "we've opened an opportunity for clever people to generate applications using our communication channels... and we are lucky to own millions of customers that can use them.

According to The Wall Street Journal: "A Spanish court found that César Alierta, chairman of Telefónica SA, enriched himself through insider trading before he joined the telecom company, but it acquitted him on the ground that the statute of limitations had run out".