| Incumbent: | 1939–1940 |
| Government Head Title: | Prime Minister |
| Government Head: | Neville Chamberlain |
| Government Head History: | 1937–1940 |
| State Head Title: | Monarch |
| State Head: | George VI |
| Total Number: | 98 appointments |
| Legislature Status: | Majority (coalition) 428 / 615 (70%) |
| Legislature Term: | 37th UK Parliament |
| Opposition Party: | Labour Party |
| Opposition Leader: | Clement Attlee |
| Outgoing Formation: | Norway Debate |
| Previous: | Fourth National Government |
| Successor: | Churchill war ministry |
Neville Chamberlain formed the Chamberlain war ministry in 1939 after declaring war on Germany. Chamberlain led the country for the first eight months of the Second World War, until the Norway Debate in Parliament led Chamberlain to resign and Winston Churchill to form a new ministry.
On 3 September 1939, Neville Chamberlain, Prime Minister of the United Kingdom, reconstructed his existing government so as to be suited for the Second World War. The most dramatic change to the ministerial line-up saw the return of Winston Churchill as First Lord of the Admiralty. Other changes included Lord Caldecote replacing Lord Maugham as Lord Chancellor, Sir John Anderson replacing Sir Samuel Hoare as Home Secretary (Hoare became Lord Privy Seal with a wide-ranging brief) and the return of Anthony Eden to the government as Secretary of State for Dominion Affairs. However, the administration was not a true national unity government as it was made up primarily of Conservatives with support from some National Labour and National Liberal members. There were no representatives from the Labour Party or Liberal Party[1]
The government was notable for having a small war cabinet consisting of only the principal and service ministers, with most other government positions serving outside the Cabinet. The War Cabinet included Chamberlain, Hoare, Chancellor of the Exchequer Sir John Simon, Foreign Secretary Lord Halifax, Churchill, Secretary of State for Air Sir Kingsley Wood, Minister for Coordination of Defence Lord Chatfield, Lord Hankey (as Minister without Portfolio), and Secretary of State for War Leslie Hore-Belisha. Oliver Stanley replaced Hore-Belisha in January 1940 while Chatfield left the war cabinet in April 1940.
The government ended on 10 May 1940 when Chamberlain resigned and was succeeded by Churchill who formed the War Coalition.
Upon the outbreak of the war, Chamberlain carried out a fullscale reconstruction of the government and introduced a small War Cabinet who were as follows:
Members of the Cabinet are in bold face.