Theodore Lyman III (August 23, 1833 – September 9, 1897) was a natural scientist, military staff officer during the American Civil War, and United States Representative from Massachusetts.

The first Theodore, Lyman's grandfather, founded a successful shipping firm in the 1790s in York, Maine, that provided the basis for the family fortune.

Theodore, Sr, sought out noted Salem architect, Samuel McIntire, to design and build his country seat, known as the Vale, in the Boston suburb of Waltham.

Mayor Lyman (Theodore, Jr.) served two terms and retired from public office in 1836 upon the sudden death of his wife Mary.

His older sister Cora inherited the town house on Beacon Hill, and the two split stocks and investment income amounting to $430,000.

Theodore then entered the University's Lawrence Scientific School and studied under professor Louis Agassiz, one of the preeminent natural scientists of the 19th century.

Colonel Robert Gould Shaw, commander of the famed 54th Massachusetts Infantry (portrayed in the movie "Glory"), was Mimi's first cousin.

Lyman returned to the United States in May 1863 and joined the staff of Major General George G. Meade as an aide-de-camp with a commission as lieutenant-colonel from Governor Andrew of Massachusetts.

During his life, Theodore Lyman acquired hundreds of acres of land on Buttermilk Bay, Cape Cod, to preserve the spawning grounds of the ocean running red brook trout.