Yitzhak Shamir (help·info) (Hebrew: יִצְחָק שָׁמִיר‎, born October 15, 1915) was Prime Minister of Israel from 1983 to 1984 and again from 1986 to 1992.

Yitzhak Shamir (Icchak Jeziernicky) was born in Ruzhany (Polish: Różana), Russia later Poland. He studied at a Hebrew High School in Białystok, Poland. As a youth he joined Betar, the Revisionist Zionist youth movement. He studied at the law faculty of Warsaw University, but cut his studies short to immigrate to what was then the British Mandate of Palestine. In 1935, after settling in Palestine, he Hebraized his surname to Shamir. He joined the Irgun Zvai Leumi, an underground Jewish militia organization that opposed British control of Palestine. When the Irgun split in 1940, Shamir sided with the more militant faction, Lehi, headed by Avraham Stern. In secret contacts with German representatives at Beirut the group offered to open up a military front against the British in the Middle East in return for the expulsion (rather than extermination) of the Jewish population of Europe to Palestine.

In 1941 Shamir was imprisoned by British authorities. After Stern was killed by the British in 1942, Shamir escaped from the detention camp and became one of the three leaders of the group in 1943, reforming it as "Lehi". In October 1944 he was exiled and interned in Africa by the Mandate authorities. He made an attempt to escape from one of the camps by hiding in a water tank. He was returned, along with the other detainees, after the Israeli Declaration of Independence in 1948. As one of Lehi's triumvirate, he authorized the assassination of the United Nations representative in the Middle East, Count Folke Bernadotte, who was seen by Shamir and his collaborators as an anti-Zionist and "an obvious agent of the British enemy".