Pirahã (also spelled Pirahá, Pirahán), or Múra-Pirahã, is the indigenous language of the isolated Pirahã people of Amazonas, Brazil. The Pirahã live along the Maici River, a tributary of the Amazon River.
Pirahã is the only surviving dialect of the Mura language, all others having become extinct in the last few centuries, as most groups of the Mura people have shifted to Portuguese. Suspected relatives, such as Matanawi, are also extinct. It is estimated to have between 250 and 380 speakers. It is not in immediate danger of extinction, as its use is vigorous and the Pirahã community is mostly monolingual.
The Pirahã language is most notable as the subject of various controversial claims; for example, that it provides evidence for linguistic relativity. The controversy is compounded by the sheer difficulty of learning the language; the number of linguists with field experience in Pirahã is very small.