The 1940 Croydon North by-election was a parliamentary by-election held in the House of Commons constituency of Croydon North on 19 June 1940. The seat had become vacant when the Conservative Member of Parliament Glyn Mason had resigned. Mason had held the seat since the 1922 general election.
During World War II, the major parties had formed a Coalition Government and agreed an electoral pact, whereby they would not contest by-elections in seats held by the other parties in the government. However, there was nothing to prevent other candidates from standing, and A. L. Lucas stood in Croydon North as an independent candidate.
Despite a very low turnout, the Conservative candidate Henry Willink held the seat for his party with a large majority. Lucas forfeited his deposit.
Election results.
! scope="col" colspan="2" style="width: 130px"|Party
! scope="col" style="width: 17em"|Candidate
! scope="col" style="width: 5em"|Votes
! scope="col" style="width: 3.5em"|%
! scope="col" style="width: 3.5em"| ;templatestyles src="Template:Tooltip/styles.css" / ;±%
! colspan="3" style="text-align: right; margin-right: 0.5em" | Majority
! colspan="3" style="text-align: right; margin-right: 0.5em" scope=row | Turnout
! colspan="3" style="text-align:right;" scope=row | Registered electors
! style="text-align:right;" | Swing
! scope="col" colspan="2" style="width: 130px"|Party
! scope="col" style="width: 17em"|Candidate
! scope="col" style="width: 5em"|Votes
! scope="col" style="width: 3.5em"|%
! scope="col" style="width: 3.5em"| ;templatestyles src="Template:Tooltip/styles.css" / ;±%
! colspan="3" style="text-align: right; margin-right: 0.5em" | Majority
! colspan="3" style="text-align: right; margin-right: 0.5em" scope=row | Turnout
! colspan="3" style="text-align:right;" scope=row | Registered electors
! style="text-align:right;" | Swing