British Sign Language (BSL) is a sign language used in the United Kingdom and is the first or preferred language among the deaf community in the UK. While private correspondence from William Stokoe hinted at a formal name for the language in 1960, the first usage of the term "British Sign Language" in an academic publication was likely by Aaron Cicourel. Based on the percentage of people who reported 'using British Sign Language at home' on the 2011 Scottish Census, the British Deaf Association estimates there are 151,000 BSL users in the UK, of whom 87,000 are Deaf. By contrast, in the 2011 England and Wales Census 15,000 people living in England and Wales reported themselves using BSL as their main language. People who are not deaf may also use BSL, as hearing relatives of deaf people, sign language interpreters or as a result of other contact with the British Deaf community. The language makes use of space and involves movement of the hands, body, face and head.

Sign languages are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign languages are full-fledged natural languages with their own grammar and lexicon. Sign languages are not universal and are usually not mutually intelligible, although there are also similarities among different sign languages.