| Election Name: | 1916 Pahiatua by-election |
| Country: | New Zealand |
| Flag Year: | 1916 |
| Type: | By-election |
| Ongoing: | no |
| Previous Election: | 1914 New Zealand general election |
| Previous Year: | 1914 general |
| Next Election: | 1919 New Zealand general election |
| Next Year: | 1919 general |
| Turnout: | 3,197 |
| Candidate1: | Harold Smith |
| Party1: | Reform Party (New Zealand) |
| Popular Vote1: | 1,521 |
| Percentage1: | 47.57 |
| Candidate2: | Robert Ross |
| Party2: | New Zealand Liberal Party |
| Popular Vote2: | 1,438 |
| Percentage2: | 44.97 |
| member | |
| Before Election: | James Escott |
| After Election: | Harold Smith |
| Before Party: | Reform Party (New Zealand) |
| After Party: | Reform Party (New Zealand) |
| Result: | Reform hold |
The Pahiatua by-election of 1916 was a by-election held in the electorate during the 19th New Zealand Parliament, on 17 August 1916. It was caused by the death of incumbent MP James Escott of the Reform Party on 28 July, and was won by Harold Smith with a majority of 420.
The following table gives the election results: