British English, or UK English (BrE, BE, en-GB), is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere. The Oxford English Dictionary applies the term to English "as spoken or written in the British Isles; esp[ecially] the forms of English usual in Great Britain...", reserving "Hiberno-English" for "The English language as spoken and written in Ireland".

There are slight regional variations in formal written English in the United Kingdom (for example, although the words wee and little are interchangeable in some contexts, one is more likely to see wee written by someone from northern Britain (and especially Scotland) or from Northern Ireland than by someone from Southern England or Wales). Nevertheless, there is a meaningful degree of uniformity in written English within the United Kingdom, and this could be described as "British English". The forms of spoken English, however, vary considerably more than in most other areas of the world where English is spoken, and a uniform concept of "British English" is therefore more difficult to apply to the spoken language. According to Tom McArthur in the Oxford Guide to World English (p. 45), "[f]or many people...especially in England [the phrase British English] is tautologous," and it shares "all the ambiguities and tensions in the word British, and as a result can be used and interpreted in two ways, more broadly or more narrowly, within a range of blurring and ambiguity".