Events from the year 1786 in Great Britain.
- 1 January – Dixon Denham, explorer (died 1828)
- 26 January – Benjamin Haydon, painter and writer (suicide 1846)
- 1 April – Fowell Buxton, brewer, politician, abolitionist and social reformer (died 1845)
- 17 April – William King, physician and philanthropist (died 1865)
- 9 May – James Foster, ironmaster (died 1853)
- 9 June – William George Horner, mathematician (died 1837)
- 5 July – Charles Alfred Stothard, draughtsman (died 1821)
- 24 September – Granville Waldegrave, naval officer (died 1857)
- 26 September – Gordon Bremer, rear admiral (died 1850)
- 2 November – Anne Knight, social reformer (died 1862)
- 29 November – Fairfax Moresby, Calcutta-born admiral of the fleet (died 1877)
- 11 December – William John Bankes, MP, explorer and Egyptologist (died 1855 in exile)
- Unknown date
- 19 January – John Duncombe, writer (born 1729)
- 25 February – Thomas Wright, astronomer, mathematician, instrument maker, architect, garden designer, antiquary and genealogist (born 1711)
- 10 April – John Byron, Vice Admiral (born 1723)
- 21 June – George Hepplewhite, furniture maker (born 1727)
- July – Josiah Martin, colonial governor (born 1737)
- 18 October – Alexander Wilson, mathematician (born 1714)
- 31 October – Princess Amelia of Great Britain (b. 1711)[9]
Palmer, Alan; Palmer, Veronica (1992). The Chronology of British History. London: Century Ltd. pp. 230–231. ISBN 0-7126-5616-2.
Greeves, Tom (1987). "The Great Courts or Parliaments of the Devon Tinners". Report & Transactions of the Devonshire Association for the Advancement of Science. 119: 143–66.