A native speaker is someone who speaks a language as his or her first language or mother tongue. Native speakers can often speak the language well since it was part of their childhood development. A native speaker's language is usually the language their parents speak and/or the language of their country of origin. It is the only language of a monolingual person, and likely the first language of a multilingual person which is acquired naturally in their native environment and which serves as the basis for their sociolinguistic identity.
It is also a term used to describe native English-speaking language instructors who teach English in non-English speaking countries.