The South Londonderry by-election of 1916 was held on 22 May 1916. The by-election was held due to the resignation of the incumbent Irish Unionist MP, John Gordon. It was won by the Irish Unionist candidate Denis Henry (a Catholic).
It was the first by-election to be held in Ireland after the Easter rebellion, and the rebellion had had no discernible impact on the contest.
References
South Londonderry by-election, 1916 Wikipedia(Text) CC BY-SA