The 1978 Earlwood state by-election was held on 15 July 1978 to elect the member for Earlwood in the New South Wales Legislative Assembly, following the resignation of Liberal MP and former premier Sir Eric Willis.
The seat was gained by Labor candidate Ken Gabb, who became the youngest member of the Parliament of New South Wales at the age of 28. Gabb defeated seven candidates, including future talkback host and Australia national rugby union team coach Alan Jones, who contested the by-election for the Liberals.
Gabb retained the seat three months later at the "Wranslide" state election on 7 October 1978, where he again defeated Jones and independent candidate Charles Bingle.
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;" | Total formal votes
! colspan="3" style="text-align:right;" | Informal votes
! colspan="3" style="text-align: right; margin-right: 0.5em" scope=row | Turnout
References.
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