The 1887 St Austell by-election was a by-election held on 18 May 1887 for the British House of Commons constituency of St Austell in Cornwall.
The by-election was triggered by the resignation of the serving Liberal Party Member of Parliament (MP), William Copeland Borlase. It was retained by the Liberal candidate William Alexander McArthur.
Result.
! 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"|%
! scope="col" style="width: 3.5em"| ;templatestyles src="Template:Tooltip/styles.css" / ;±%
! colspan="3" style="text-align: right; margin-right: 0.5em" | Majority
! colspan="3" style="text-align: right; margin-right: 0.5em" scope=row | Turnout
! style="text-align:right;" | Swing
References.
 ;templatestyles src="Reflist/styles.css" / ;