The United Kingdom has no official language. English is the main language and the de facto official language, spoken monolingually by an estimated 95% of the UK population.
However, two of the UK's nations do have official languages. In Wales, English and Welsh are both official and in Northern Ireland, English, Irish and Ulster Scots are official.
Under the European Charter for Regional or Minority Languages the UK government recognizes the status of certain languages. Welsh, Scottish Gaelic and Cornish are recognised as having equal status with English in Wales, Scotland and Cornwall respectively. Other native languages include Irish (in Northern Ireland), Scots in Scotland and Ulster Scots (Northern Ireland) and British Sign Language.
According to the most recent census, Welsh is spoken by about 20% of the population of Wales (around 600,000 speakers). However there is some controversy over the number who actually do speak Welsh. Some statistics choose to include people who have studied Welsh to at least GCSE standard, not all of whom could strictly speaking be regarded as fluent speakers of the language. The Welsh language has for a long time been embroiled in politics related to Welsh nationalism. This makes it harder to get an accurate and unbiased figure for how many people actually speak the language fluently.
Scottish Gaelic has about 60,000 speakers (roughly 1% of the population of Scotland). In Northern Ireland about 7% of the population speak Irish Gaelic (around 20,000 speakers). Cornish is spoken by roughly 3,500 people (about 0.6% of the population of Cornwall). British Sign Language is understood by less than 0.1% of the total population of the UK.