Muselmann (German plural Muselmänner) was a term used amongst prisoners of German Nazi concentration camps during the Holocaust of World War II to refer to those suffering from a combination of starvation (known also as "hunger disease") and exhaustion, as well as those who were resigned to their impending death. The Muselmann prisoners exhibited severe emaciation and physical weakness, an apathetic listlessness regarding their own fate, and unresponsiveness to their surroundings owing to their barbaric treatment.

Some scholars argue that the term possibly comes from the Muselmanns' inability to stand for any time due to the loss of leg muscle, thus leading them to spend much of their time in a prone position.

"Muselmann" also literally means "a Muslim" in Yiddish and a number of other languages (albeit with spelling differences) and ultimately derives from the Old Turkish word for Muslim, مسلمان (müsliman).^{[citation needed]} In the context of this article, "Muselmann" seemingly derives from the German: Muselman, a historical term for "Muslim" (literally "mussulman"), which is now considered derogatory. If this derivation is correct, "Muselmann" would literally mean "Muslim man" (Muselman + Mann); but how this term later came to be used to denote starving concentration camp prisoners is uncertain. Some scholars argue that the term may derive from the Muselmann's inability to stand due to a combination of exhaustion and starvation-induced muscular atrophy in their legs, thus forcing them to spend much of their time in a prone position, which may have evoked the image of the Muslim practice of prostration during prayer, called sujud.

Viktor Frankl, who survived internment in the Auschwitz-Birkenau concentration camp, wrote in his memoirs that the term was first used by camp's prisoners to refer to the Kapos—prisoners assigned to supervise forced labor by the SS guards—as, to them, the term "Muslim" carried a connotation of barbarism. On the other hand, Eugen Kogon, who survived internment in Buchenwald, wrote that the term originated from Nazi staff-members, who ascribed the Muselmann's apparent apathy to their circumstances (likely the result of weakness and acute hunger) to Islamic fatalism.

Other theories as to the term's origins completely eschew any intimate connection to the notions of Islam, as even by the outbreak of World War II, the term "Muselman" was considered archaic and was rarely used to refer to Muslims. Marie Jalowicz-Simon, a philologist who also survived Nazi persecution, argued that by the 1940s, Muselmann had become a colloquial term for the elderly or infirm, which allowed it to be co-opted into the Nazi vocabulary.

The American psychologist David P. Boder identified the term "Musselman" in 1946 while interviewing camp survivors in Europe. He asked them to describe, spell, and pronounce the word for camp inmates so emaciated that they had lost the will to live.

Primo Levi tried to explain the term (he also uses "Musselman") in a footnote of If This Is a Man (the commonly found English translation is titled Survival in Auschwitz), his autobiographical account of his time in Auschwitz:

This word 'Muselmann', I do not know why, was used by the old ones of the camp to describe the weak, the inept, those doomed to selection.