He graduated in law at the University of Turin in 1931 and the following year entered the Italian diplomatic service.
He was Italian Ambassador to the United Nations (1958–1961) and Ambassador to the United States (1967–1975). In 1937 he was posted to the Italian embassy in London, where he worked for the ambassadors Dino Grandi and Giuseppe Bastianini. From 1940 to 1943 Ortona worked in the latter’s offices in Zadar, where Bastianini was appointed governor, and in Rome where Bastianini was undersecretary for foreign affairs under Benito Mussolini.
Ortona’s diaries from this period, which he published as Diplomazia di guerra.
In November 1944 he was appointed to a delegation seeking economic assistance from the United States for the post-war reconstruction of Italy. Ortona returned to Italy in 1961 becoming Director General of Economic Affairs at the Ministry of Foreign Affairs and then Secretary General of the Ministry itself.
In 1967 Ortona was appointed Italian ambassador in Washington, a post which he held for the next eight years. In 1975 Ortona, aged 65, retired from the diplomatic service.
He took on posts as president of Honeywell’s Italian businesses, of Aeritalia and of Confitarma (Confederazione italiana armatori).
He also became president of the Istituto per gli Studi di Politica Internazionale (Institute for International Policy Studies) and published several volumes of his diaries which together cover the years 1937–1975. Egidio Ortona died in Rome on 10 January 1996 at the age of 85. He was buried in Casale Monferrato where, on 16 March 2007, the public gardens of the Piazza Martiri della Libertà near the house where he was born were officially dedicated to him.
In this period he played an instrumental role in the successful signing of the Ussr-Fiat deal that marked the beginning of private mass motorization in the leading socialist State.
He remained in Washington at the Italian Embassy until, in 1958, he was appointed as Italy’s Ambassador to the United Nations, remaining in the job for a little over two years, during which period Italy was a non-permanent member of the Security Council.
Married Giulia Rossi in 1935.