The 1915 Arfon by-election was a parliamentary by-election held on 6 July 1915 for the Arfon division of Caernarvonshire in North Wales, a constituency of the British House of Commons.
The by-election was caused by death at the age of 55 of the Liberal Member of Parliament (MP) William Jones, a Junior Lord of the Treasury in H. H. Asquith's Liberal government, who had held the seat since the 1895 general election.
The only candidate nominated to contest the by-election was the Liberal Caradoc Rees, who was therefore elected unopposed. Rees, who was a solicitor, held the seat until the constituency was abolished at the general election in December 1918 and was later appointed as a judge.
! scope="col" colspan="2" style="width: 130px"|Party
! scope="col" style="width: 17em"|Candidate
! scope="col" style="width: 5em"|Votes
! scope="col" style="width: 3.5em"|%
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! colspan="3" style="text-align:right;" scope=row | Registered electors
References.
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