| Ebenezer Thayer, Jr. | |
| Birth Date: | August 21, 1746 |
| Death Date: | May 30, 1809 (aged 62) |
| Occupation: | Farmer |
| Spouse: | Rachel Thayer, m. December 19, 1772 |
| Title1: | Norfolk County, Massachusetts Sheriff |
| Term Start1: | 1793 |
| Term End1: | 1794 |
| Predecessor1: | New office |
| Successor1: | Atherton Thayer |
| Allegiance: |  United States |
| Serviceyears: | Militia |
| Commands: | Massachusetts provincial militia |
Ebenezer Thayer, Jr. (August 21, 1746 – May 30, 1809) was a Massachusetts farmer, military officer, town official, and politician who served in both branches of the Massachusetts legislature, as a member of the Massachusetts Governor's Council; and, from 1793 to 1794, as the first sheriff of Norfolk County, Massachusetts.
The Braintree Instructions, drafted by John Adams, were addressed to Thayer's father, Ebenezer Thayer, Esq., from his constituents in Braintree.
During the American Revolutionary War Thayer was active in recruiting men in his home town and in leading them in the war.
His half-brother was Atherton Thayer.
Over a number of generations the Thayer family became known as a Boston Brahmin family and descended from early settlers and brothers Thomas Thayer (1596–1665) and Richard Thayer (1601–1664).[1]