The St Albans by-election of 1943 was a parliamentary by-election held in England in October 1943 for the House of Commons constituency of St Albans in Hertfordshire.
The by-election was held to fill the vacancy caused when the town's Conservative Party Member of Parliament (MP) Sir Francis Fremantle died suddenly at home on 26 August, aged 71. Fremantle had held the seat since a by-election in 1919.
The Conservative Party nominated as its candidate, 31-year-old John Grimston, who was then serving in the Royal Air Force. Grimston was the son and heir of 4th Earl of Verlam, and a cousin of the Assistant Postmaster-General Robert Grimston MP.
In accordance with an electoral truce between the parties in the wartime coalition government, neither the Liberal nor Labour parties nominated a candidate.
However, the dramatist William Douglas-Home, who was then an officer of the Royal Armoured Corps and an opponent of the policy of requiring the unconditional surrender of Nazi Germany, announced that he would stand as an independent candidate.