Karski was among the first to provide first-hand accounts of the Holocaust to the world, Obama said when announcing the selection during a speech Monday at the Holocaust Memorial Museum in Washington.
The Medal of Freedom, the highest civilian honor, presented to individuals who made particularly meritorious contributions to the security or national interests of the United States, to world peace, or to cultural or other significant public or private endeavors, the White House said in a release.
During World War II, Karski worked as a courier, entering the Warsaw ghetto and the Nazi Izbica transit camp, where he witnessed atrocities occurring under Nazi occupation, the White House said. Karski later traveled to London to meet with the Polish government-in-exile and British officials. He eventually went to the United States and met with President Franklin D. Roosevelt.
Karski published "Story of a Secret State," earned a doctorate at Georgetown University and became a professor at Georgetown's School of Foreign Service. Born in 1914, Karski became a U.S. citizen in 1954 and died in 2000.
Other Medal of Freedom recipients will be announced during the coming weeks. The awards will be presented at a White House ceremony later in the spring.