The 1917 Bay of Islands by-election was a by-election held on 19 March 1917 during the 19th New Zealand Parliament in the Northland electorate of Bay of Islands. The by-election came about because Vernon Reed's win in the 1914 general election had been declared void by an electoral court, and Reed barred from standing for a year. The seat was won by William Stewart, Reed's Reform Party colleague, in the resulting 1915 by-election. When Reed became eligible again, Stewart resigned and Reed won the 1917 by-election unopposed.