Events from the year 1938 in the United Kingdom.
- 6 January – psychoanalyst Sigmund Freud arrives in London having fled from Vienna in Austria.
- 17 January – Joseph P. Kennedy, Sr., is appointed United States Ambassador to the United Kingdom.
- 20 February – Anthony Eden resigns as Foreign Secretary, over Chamberlain's policy towards Italy. Lord Halifax takes over.
- 16 April – Anglo-Italian Treaty: Britain recognises Italian government over Ethiopia, in return for Italian troops withdrawing from Spain.
- 23 April – York Castle Museum opened.
- 25 April – Anglo-Irish Trade Agreement with the Republic of Ireland settles trade disputes and agrees to the Royal Navy abandoning the British sovereign bases at the Treaty ports in Ireland.
- 3 May – Empire Exhibition opens in Glasgow.
- 10 May – an underground explosion at Markham Colliery, near Staveley, Derbyshire, kills 79.
- 1 June – the Bren light machine gun comes into service with the British Army.
- 2 June – the children's zoo at London Zoo is opened by Robert and Ted Kennedy, two of the sons of United States ambassador Joseph P. Kennedy.
- 18 June – Women's Voluntary Service founded to assist the Civil Defence Service.
- 3 July – the London and North Eastern Railway's streamlined Class A4 4468 Mallard reaches a speed of 126 mph (203 km/h), the highest certified speed for a steam locomotive.
- 9 July – gas masks are issued to the civilian population.
- 24 June – Test cricket is televised for the first time.
- 11 July – 3 October: military installations at the Treaty Ports in the Republic of Ireland (Berehaven, Spike Island at Queenstown, and Lough Swilly) are handed over from British control to the Government of Ireland, under terms of the Anglo-Irish Trade Agreement ratified by the Eire (Confirmation of Agreements) Act earlier in the year.
- 30 July – The Beano comic first goes on sale, featuring the character Lord Snooty.
- August – Muslims protest in London about passages they consider disrespectful of their religion in H. G. Wells' A Short History of the World (1922).
- 13–20 August – Great Britain and the United States contest the inaugural Amateur World Series in baseball, played in the north of England. Britain wins every match.
- 23 August – English cricketer Len Hutton scores a record Test score of 364 runs in a match against Australia.
- 9 September – Auxiliary Territorial Service, as a women's voluntary service.
- 13 September – Prime Minister Neville Chamberlain meets German Chancellor Adolf Hitler in an attempt to negotiate an end to German expansionist policies.
- 27 September – RMS Queen Elizabeth is launched at Clydebank; she is the largest ship in the world at this time.
- 29 September – Chamberlain signs the Munich Agreement; and a resolution with Germany determining to resolve all future disputes between the two countries through peaceful means.
- 30 September – Neville Chamberlain returns to the UK from Munich, at Heston Aerodrome memorably waving the resolution signed the day earlier with Germany, and later in Downing Street giving his famous Peace for our time speech. George VI and Queen Elizabeth appear with Chamberlain on the balcony of Buckingham Palace to celebrate the agreement.
- 1 October – Picture Post magazine first published.
- 29 October – City Hall, Norwich, designed in the Art Deco style by C. H. James and S. R. Pierce, is opened.
- 21 November – Apostolic Delegation to Great Britain appointed.
- 1–2 December – first Kindertransport from Berlin to London Liverpool Street station via Harwich.
- 16 December – aircraft carrier HMS Ark Royal (91) (launched by Cammell Laird in Birkenhead in 1937 under the 1934 build plan) is commissioned into the Royal Navy.
- 2 January
- 26 February – Brian Kilby, marathon runner
- 11 January – Arthur Scargill, Trade Union leader
- 14 March – Eleanor Bron, actress and author
- 6 April – Paul Daniels, magician (died 2016)
- 9 May – Geoffrey Holland, English civil servant and academic
- 31 May – John Prescott, Deputy Prime Minister
- 20 July – Diana Rigg, actress
- 22 July – Terence Stamp, actor
- 29 July – Tom Raworth, poet (died 2017)
- 6 August – Rees Davies, historian (died 2005)
- 25 August – Frederick Forsyth, writer
- 30 August – Alf Meakin, track and field athlete
- 20 October – Iain MacMillan, photographer (died 2006)
- 22 October – Derek Jacobi, actor
- 28 October – David Dimbleby, broadcaster
- 1 November – Malcolm Laycock, radio presenter and producer (died 2009)
- 12 November – Terry McDonald, footballer and coach
- 27 November – Rodney Bewes, comedy actor
- 4 December – Richard Meade, equestrian (died 2015)
- 15 December – Michael Bogdanov, theatre director (died 2017)
- 17 December – Carlo Little, drummer (died 2005)
- 21 December – John Quayle, actor
- John Bulmer, documentary photographer and filmmaker