| Barzillai Gannett | |
| State: | Massachusetts |
| Term Start: | March 4, 1809 |
| Term End: | 1812 |
| Preceded: | John Chandler |
| Office2: | Member of the Massachusetts State Senate |
| Term Start2: | 1807 |
| Term End2: | 1807 |
| Office3: | Member Board of Selectmen and Assessors Gardiner Maine |
| Term Start3: | March 21, 1803 |
| Term End3: | 1804 |
| Office4: | Member Surveyors of HIghwayas Gardiner Maine |
| Term Start4: | March 21, 1803 |
| Term End4: | 1804 |
| Office5: | Town Clerk Pittston, Maine |
| Term Start5: | 1794 |
| Term End5: | 1795 |
| Preceded5: | Seth Gay |
| Succeeded5: | Seth Gay |
| Office6: | Member of the Massachusetts House of Representatives |
| Term6: | 1805-1806 |
| Birth Date: | 17 June 1764 |
| Birth Place: | Bridgewater, Province of Massachusetts Bay, British America |
| Death Place: | New York City, New York, U.S. |
| Spouse: | Elizabeth Farley |
| Alma Mater: | Harvard University |
Barzillai Gannett (June 17, 1764 – 1832) was a U.S. Representative from Massachusetts.
Born in Bridgewater in the Province of Massachusetts Bay, Gannett was graduated from Harvard University in 1785. He studied theology, but did not enter the ministry. He served as Selectman of Pittston, Maine (then a district of Massachusetts). He also served as town clerk in 1794 and town moderator 1797–1802. Gannett was Selectman and assessor of Gardiner, Maine from 1803 to 1808. He was appointed as the first postmaster of Gardiner and served from September 30, 1804, to October 1, 1809. He also served as Town Moderator. Gannett served as member of both the Massachusetts House of Representatives and the Massachusetts State Senate.
Gannett was elected as a Democratic-Republican to the Eleventh and Twelfth Congresses and served from March 4, 1809, until his resignation in 1812.
Because of an accusation regarding a breach of trust Gannett left Maine, changed his name to Benjamin Gardiner, and moved to Ohio.
During about the year 1822 Barzillai Gannett (Benjamin Gardiner) again suddenly disappeared from Ohio.
Gannett died in New York City in 1832.