Thomas Hill (January 7, 1818[2] – November 21, 1891[3]) was an American Unitarian clergyman, mathematician, scientist, philosopher, and educator.

His father taught him botany, and he took a delight in nature and devised scientific instruments, one that calculated eclipses and was subsequently awarded the Scott Medal by the Franklin Institute.

Ill health caused his retirement from Harvard, but he was able to serve as official botanist during the Hassler Expedition circumnavigating South America through the Magellan Strait from Boston in December 1871 to San Francisco in August 1872.

[5] Hill claimed to have injured his testicle while gardening, an incident that made him wary of laboratory instruction at Harvard, warning students not to exert themselves too much in their studies.

[6] Hill's home in Waltham, Massachusetts, where he began his career, is listed on the National Register of Historic Places.