Born in Yamaguchi Prefecture, Satō was a member of the Satō–Kishi–Abe family and the younger brother of prime minister Nobusuke Kishi.

[2] Satō studied German law at Tokyo Imperial University and in 1923, passed the senior civil service examinations.

Sato gradually rose through the ranks of Japanese politics, becoming chief cabinet secretary to then prime minister Shigeru Yoshida from January 1953 to July 1954.

[5] He would go on to serve the longest stint of any prime minister up until that time, and by the late 1960s he appeared to have single-handed control over the entire Japanese government.

While visiting the United States in January 1965, Satō openly asked President Lyndon Johnson to return Okinawa to Japan.

[9] Accordingly, Satō introduced the Three Non-Nuclear Principles on 11 December 1967, promising the non-production, non-possession, and non-introduction of nuclear weapons inside Japan.

Therafter, Satō shepherded Japan's entery into the Nuclear Non-Proliferation Treaty and the Diet passed a resolution formally adopting the Non-Nuclear Principles in 1971.

In December 2008, the Japanese government declassified a document showing that during a visit to the US in January 1965, he was discussing with US officials the possibility of using nuclear weapons against the People's Republic of China.

[10] In December 2009, his son reported that his father agreed in a November 1969 conversation with US President Nixon to allow the stationing of nuclear warheads in Okinawa even after it was restored to Japanese sovereignty.

[11] Overcrowded universities, increasing student radicalization, hopes for an abrogation of the US-Japan Security Treaty after its initial 10-year term ended in 1970, and growing opposition to Japan's material and ideological support for America's war in Vietnam helped precipitate large scale protests at hundreds of Japanese schools and universities in 1968–1969, part of a worldwide protest cycle in 1968.

After more than a year of conflict, Satō's administration responded by calling in riot police to forcibly clear the university campuses.

Thereafter, Satō allowed the Security Treaty to automatically renew in 1970, dashing the hopes of activist groups who staged large street protests in an attempt to eliminate it.

The successful resolution of the university crisis, continued robust economic growth, and above all, the 1969 announcement of the United States' commitment to return Okinawa to Japan, made Satō broadly popular with the Japanese public and allowed him to win a then unprecedented third consecutive term as prime minister.

[14] The following month, the government was again surprised to learn that, without prior consultation, Nixon was imposing a 10 percent surcharge on imports, a decision explicitly aimed at hindering Japan's exports to the United States, and was unilaterally suspending the convertibility of dollars into gold, which would eventually lead to the collapse of the Bretton Woods system of fixed currency exchange rates.

Upon leaving the premiership in 1972 to an approval rating of 19% (by April) and a fractured party, Satō moved back to his home in Setagaya Ward, Tokyo, staying out of the eyes of the media but remaining in the Diet.

His reputation, however, quickly began to be rehabilitated, starting in November of that year with his awarding of the Grand Cordon of the Supreme Order of the Chrysanthemum.

Satō opened up to the media after the award, with outlets noting his visual image change, with a longer hairstyle reminiscent of the post-presidency of Lyndon B.

[16] Upon returning to Japan, his successor, the initially-popular Kakuei Tanaka, who had been handed a rebuke with 17 seat losses in the 1972 Japanese general election, looked to Satō to repair relations within the LDP, especially towards his rival Takeo Fukuda.

[20] In April 1975, as part of his last foreign visit before his death, Satō was chosen as the LDP representative to attend the funeral of Chiang Kai-Shek.

Shinji's son-in-law, Masashi Adachi, currently serves in the House of Councillors, and formerly worked as an aide for his cousin-in-law, Eisaku's grandnephew, Shinzo Abe.