Thomas Wintringham Liberal Margaret Wintringham Liberal The 1921 Louth by-election was a by-election held on 22 September 1921 for the British House of Commons constituency of Louth in Lincolnshire.

The seat had become vacant following the death of the Liberal Member of Parliament (MP) Thomas Wintringham on 8 August 1921.

Despite rumours the contrary, on 13 September nominations closed to confirm that the election would be a three-way contest.

Wintringham held the seat that her husband had gained for the Liberals in a by-election the year before.

Wintringham become only the second woman to take her seat in the House of Commons, and the first female Liberal MP.