Owen Thomas Independent Labour Robert Thomas Liberal The 1923 Anglesey by-election was a parliamentary by-election for the British House of Commons constituency of Anglesey on 7 April 1923.

The by-election was caused by the death of the sitting Labour MP, Sir Owen Thomas on 17 January 1923.

Anglesey had been won by either the Liberal Party or the Whigs at every election since 1784, until Thomas surprisingly gained it as an independent Labour candidate in 1918.

The result at the last General Election was as follows; Labour's campaign was supported by visits from national figures such as Arthur Henderson, and a host of Labour MPs from south Wales such as David Watts Morgan, Tom Griffiths, David Grenfell and T. I. Mardy Jones, as well as prominent Welsh nationalist figures such as future Liberal MP William John Gruffydd and Principal Thomas Rees.

John called for Welsh Home Rule, even though it was not Labour Party policy.