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.

Sir Alexander Sprot, 1st Baronet, was a British soldier and Scottish Unionist Party politician. He served in the Second Anglo-Afghan War, the Second Boer War and World War I. During his political career, he represented the constituencies of East Fife and North Lanarkshire.