| Election Name: | 1939 Monmouth by-election |
| Country: | United Kingdom |
| Type: | Parliamentary |
| Vote Type: | Popular |
The 1939 Monmouth by-election was a by-election held for the British House of Commons constituency of Monmouth in Wales on 25 July 1939.
The Conservative MP John Herbert had resigned his seat on 1 July 1939, having been appointed as Governor of Bengal.
The Conservative candidate was 55-year-old Leslie Pym, who had not had previously contested a parliamentary election.
The Labour Party candidate at the 1935 general election had been 22-year-old Michael Foot, who later became Leader of the Labour Party. Foot did not contest the by-election, when the Labour candidate was F.R. Hancock, who had been unsuccessful in Salisbury at the 1929 general election and at a by-election in 1931. He had also been an unsuccessful candidate in Lewes at the 1931 and 1935 general elections. He was also a Quaker and thus opposed to all war.
On a slightly reduced turnout, Pym held the seat for the Conservatives, with a reduced but still large majority of 5,815.
Pym was re-elected at the 1945 general election, but died five days later.