The Croydon North by-election, 1940 was a parliamentary by-election held in the British 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. Despite a very low turnout, the Conservative candidate Henry Willink held the seat for his party with a large majority. Lucas forfeited his deposit.