Czesław Miłosz (/ˈmiːlɒʃ/ MEE-losh, US also /-lɔːʃ, -wɒʃ, -wɔːʃ/ -⁠lawsh, -⁠wosh, -⁠wawsh, Polish: [ˈt͡ʂɛswaf ˈmiwɔʂ] ^ⓘ; 30 June 1911 – 14 August 2004) was a Polish-American poet, prose writer, translator, and diplomat. He primarily wrote his poetry in Polish. Regarded as one of the great poets of the 20th century, he won the 1980 Nobel Prize in Literature. In its citation, the Swedish Academy called Miłosz a writer who "voices man's exposed condition in a world of severe conflicts".

Miłosz survived the German occupation of Warsaw during World War II and became a cultural attaché for the Polish government during the postwar period. When communist authorities threatened his safety, he defected to France and ultimately chose exile in the United States, where he became a professor at the University of California, Berkeley. His poetry—particularly about his wartime experience—and his appraisal of Stalinism in a prose book, The Captive Mind, brought him renown as a leading émigré artist and intellectual.

Throughout his life and work, Miłosz tackled questions of morality, politics, history, and faith. As a translator, he introduced Western works to a Polish audience, and as a scholar and editor, he championed a greater awareness of Slavic literature in the West. Faith played a role in his work as he explored his Catholicism and personal experience. He wrote in Polish and English.

Miłosz died in Kraków, Poland, in 2004. He is interred in Skałka, a church known in Poland as a place of honor for distinguished Poles.

Czesław Miłosz was born on 30 June 1911, in the village of Šeteniai (Polish: Szetejnie), Kovno Governorate, Russian Empire (now Kėdainiai district, Kaunas County, Lithuania). He was the son of Aleksander Miłosz (1883–1959), a Polish civil engineer, and his wife, Weronika (née Kunat; 1887–1945).

Miłosz was born into a prominent family. On his mother's side, his grandfather was Zygmunt Kunat, a descendant of a Polish family that traced its lineage to the 13th century and owned an estate in Krasnogruda (in present-day Poland). Having studied agriculture in Warsaw, Zygmunt settled in Šeteniai after marrying Miłosz's grandmother, Jozefa, a descendant of the noble Syruć family, which was of Lithuanian origin. One of her ancestors, Szymon Syruć [pl], had been personal secretary to Stanisław I, King of Poland and Grand Duke of Lithuania. Miłosz's paternal grandfather, Artur Miłosz, was also from a noble family and fought in the 1863 January Uprising for Polish independence. Miłosz's grandmother, Stanisława, was a doctor's daughter from Riga, Latvia, and a member of the German-Polish von Mohl family. The Miłosz estate was in Serbinai, a name that Miłosz's biographer Andrzej Franaszek [pl] has suggested could indicate Serbian origin; it is possible the Miłosz family originated in Serbia and settled in present-day Lithuania after being expelled from Germany centuries earlier. Miłosz's father was born and educated in Riga. Miłosz's mother was born in Šeteniai and educated in Kraków.

Despite this noble lineage, Miłosz's childhood on his maternal grandfather's estate in Šeteniai lacked the trappings of wealth or the customs of the upper class. He memorialized his childhood in a 1955 novel, The Issa Valley [pl], and a 1959 memoir, Native Realm [pl]. In these works, he described the influence of his Catholic grandmother, Jozefa, his burgeoning love for literature, and his early awareness, as a member of the Polish gentry in Lithuania, of the role of class in society.

Miłosz's early years were marked by upheaval. When his father was hired to work on infrastructure projects in Siberia, he and his mother traveled to be with him. After World War I broke out in 1914, Miłosz's father was conscripted into the Russian army, tasked with engineering roads and bridges for troop movements. Miłosz and his mother were sheltered in Vilnius when the German army captured it in 1915. Afterward, they once again joined Miłosz's father, following him as the front moved further into Russia, where, in 1917, Miłosz's brother, Andrzej, was born. Finally, after moving through Estonia and Latvia, the family returned to Šeteniai in 1918. But the Polish–Soviet War broke out in 1919, during which Miłosz's father was involved in a failed attempt to incorporate the newly independent Lithuania into the Second Polish Republic, resulting in his expulsion from Lithuania and the family's move to what was then known as Wilno, which had come under Polish control after the Polish–Lithuanian War of 1920. The Polish-Soviet War continued, forcing the family to move again. At one point during the conflict, Polish soldiers fired at Miłosz and his mother, an episode he recounted in Native Realm. The family returned to Wilno after the war ended in 1921.