Quechua is a Native American language family or macrolanguage spoken primarily in the Andes of South America, derived from an original common ancestor language, Proto-Quechua. It is the most widely spoken language family of the indigenous peoples of the Americas, with a total of probably some 6 to 8 million speakers (estimates vary widely). Some speakers of Quechua also call it 'runa simi' (or regional variants thereof), literally 'people speech', although 'runa' here has the more specific sense of indigenous Andean people.

There are few sharp boundaries between what might be identified as specific 'languages' within the Quechua family, which consists of large zones of dialect continua, although three major regions can be distinguished:

Ecuador Quechua (usually known there as 'Quichua' or 'Kichwa'), both in the highlands and the Amazon River valley, with pockets also in southern and Amazonian Peru. Central Quechua, spoken in the highlands from the Ancash to Huancayo regions in north-central Peru.
Southern Quechua, with the largest number of speakers, in all regions further south, again mostly highlands: from Huancavelica through the Ayacucho, Cuzco and Puno regions of Peru, across much of Bolivia and in pockets in north-western Argentina.

Speakers from different points within any one of these major regions can generally understand each other reasonably well. There are nonetheless significant local-level differences across each. (Huancayo Quechua, in particular, has several very distinctive characteristics that make this variety distinctly difficult to understand, even for other Central Quechua speakers.) Speakers from different major regions, meanwhile, particularly Central vs Southern Quechua, are not able to communicate effectively.

The lack of mutual intelligibility is the basic criterion that defines Quechua not as a single language, as it is often mistakenly described, but as a language family. The complex and progressive nature of how speech varies across the dialect continua zones make it nearly impossible to put a precise number on how many different Quechua languages or dialects there are; the Ethnologue lists 44. As a reference point, the overall degree of diversity across the family is a little less than that for the Romance or Germanic language families, and more of the order of Slavic or Arabic.