Caerphilly by election, 1921

The Caerphilly by-election of 1921 was held on 24 August 1921. The by-election was held due to the death of the incumbent Labour MP, Alfred Onions. It was won by the Labour candidate Morgan Jones.

Morgan Jones clinched the Labour nomination despite not being the preferred candidate of the South Wales Miners' Federation. He was the first conscientious objector to be elected to Parliament after World War I.