The Westminster St. George's by-election, 1931 was a parliamentary by-election held on 19 March 1931 for the British House of Commons constituency of Westminster St. George's.

Westminster St George's, originally named St George's, Hanover Square, was a parliamentary constituency in Central London. It returned one Member of Parliament (MP) to the House of Commons of the Parliament of the United Kingdom, elected by the first past the post system of election.