This article is about the Prime Minister of Japan. For the governor of Fukushima Prefecture of Japan of the same name, see Eisaku Satō (governor).

Eisaku Satō (佐藤 榮作, Satō Eisaku^?, March 27, 1901 – June 3, 1975) was a Japanese politician and the 39th Prime Minister of Japan, elected on November 9, 1964, and re-elected on February 17, 1967, and January 14, 1970, serving until July 7, 1972. He was the longest serving prime minister in the history of Japan.

Satō was born in Tabuse, Yamaguchi Prefecture, and studied German law at Tokyo Imperial University. In 1923, he passed the senior civil service examinations, and in the following year, upon graduation, became a civil servant in the Ministry of Railways. He served as Director of the Osaka Railways Bureau from 1944 to 1946 and Vice-Minister for Transportation from 1947 to 1948.

Satō entered the Diet in 1949 as a member of the Liberal Party.

He was appointed Minister of Postal Services and Telecommunications from July 1951 - July 1952. Sato gradually rose through the ranks of Japanese politics, becoming Chief Cabinet Secretary to Prime Minister Shigeru Yoshida from January 1953 to July 1954. He later served as Minister of Construction from October 1952-February 1953.