Thayer Academy (TA) is a private, co-educational, college-preparatory day school located in Braintree, Massachusetts, United States.

The academy, conceived in 1871 at the bequest of General Sylvanus Thayer, known as the father of the United States Military Academy at West Point, and founder of the Thayer School of Engineering at Dartmouth College, was established in 1877.

General Thayer, born in Braintree, Massachusetts, graduated as valedictorian from both Dartmouth College and the United States Military Academy at West Point, New York.

General Thayer was dedicated to hard work, and at the age of 17, he taught in the local schools of Hanover, New Hampshire to earn money to pay for college – an early sign of the importance he attached to teaching and education.

Beginning in 1969, the lower grades were gradually eliminated, and Thayerlands became Thayer Academy Middle School.