The Collared brown lemur (Eulemur collaris), also known as the red-collared brown lemur or red-collared lemur, is a medium-sized strepsirrhine primate and one of twelve species of brown lemur in the family Lemuridae. It is only found in south-eastern Madagascar. Like most species of lemur, it is arboreal, moving quadrupedally and occasionally leaping from tree to tree. Like other brown lemurs, this species is cathemeral (active during the day and the night), lives in social groups, primarily eats fruit, exhibits sexual dichromatism, and does not demonstrate female dominance. The species is listed as Endangered by the International Union for Conservation of Nature (IUCN) and is threatened primarily by habitat loss.
Together with the twelve other true lemurs (genus Eulemur), the collared brown lemur (E. collaris) is a type of lemur belonging to the family Lemuridae. Collectively, lemurs (infraorder Lemuriformes) are classified as strepsirrhine primates. Originally listed as a subspecies of the common brown lemur (E. fulvus), the collared brown lemur was promoted to full species status in 2001 by biological anthropologist Colin Groves.