Sir Alexander Sprot Unionist Jennie Lee Labour The 1929 North Lanarkshire by-election was a parliamentary by-election held in the United Kingdom on 21 March 1929 for the House of Commons constituency of North Lanarkshire in Scotland.

The by-election was caused by the death on 8 February of the constituency's Unionist Member of Parliament, Sir Alexander Sprot, who had gained the seat from Labour at the 1924 general election.

On 1 March, nationally, Liberal leader, David Lloyd George launched the Liberal programme for the upcoming General Election, titled We Can Conquer Unemployment.

The Labour Party gained the seat.