Andover Theological Seminary (1807–1965) was a Congregationalist seminary founded in 1807 and originally located in Andover, Massachusetts on the campus of Phillips Academy.

From 1908 to 1931, it was located at Harvard University in Cambridge, Massachusetts. It then collocated with Newton Theological Institution (NTI) in Newton, Massachusetts. Then, in 1965, Andover Theological Seminary and NTI formally merged in 1965 to form Andover Newton Theological School in Andover, Massachusetts. In its original and merged forms, it is the first and thus the oldest Protestant theological seminary in the United States. The seminary continues as Andover Newton Seminary at Yale Divinity School, which was launched in 2017.

Andover Theological Seminary traces its roots to the late 18th century and the desire for a well-educated clergy among Congregationalists in the United States. That desire was expressed in the founding of Phillips Academy in 1778 for "the promotion of true Piety and Virtue".

In 1806, a growing split within the Congregational churches, known as the Unitarian Controversy, came to a full boil on the campus of Harvard College. The Hollis Chair of Divinity sat empty at Harvard for two years owing to tensions between liberal and more orthodox Calvinists. This theological battle soon divided many of the oldest churches in Massachusetts and began to impact church polity and the hiring of ministers. When the Harvard Board of Overseers appointed well-known liberal^{[citation needed]} Henry Ware to the Hollis Chair in 1805, the Calvinists withdrew to organize and establish a new school in 1807, Andover Theological Seminary on the campus of Phillips Academy (est. 1778) in Andover, Massachusetts. This act, covered widely in the national press, was one of the significant events that contributed to the split in the denomination and to the eventual founding of the American Unitarian Association in 1825 (which joined the Universalists, founded in 1793, to become the Unitarian Universalist Association in 1961).

Andover was founded by the joint efforts of traditionalist, "Old Calvinists" and the adherents of the New Divinity (also known as New England theology) which was more revivalistic. Leonard Woods, Moses Stuart, and Edward Dorr Griffin were early faculty.^[1]

Between 1886 and 1892, a theological dispute known as the "Andover Controversy" broke out between the conservative "New England Calvinism" of the founders and the liberal theology of many on the faculty. President E. C. Smyth was investigated and dismissed for his liberal views in 1887, but in 1891 his dismissal was reversed, on technical grounds, by the Massachusetts Supreme Court, and the matter was dropped the following year.^[2]

In 1908, Harvard Divinity School and Andover attempted to reconcile, and the seminary moved its faculty and library to the Harvard campus^[3] (and soon into Andover Hall [1911]). Plans for a formal affiliation between the academies were made, but the Supreme Judicial Court of Massachusetts disallowed the alliance since Andover's endowment is designated for a Christian theological education. Andover, therefore, relocated to the campus of Newton Theological Institution in 1931.

Andover Theological Seminary and the Newton Theological Institution formally merged in 1965 as the Andover Newton Theological School (ANTS). Newton Theological Institution began instruction in 1825 at Newton Centre, Massachusetts as a graduate seminary formally affiliated with the group now known as American Baptist Churches USA, the oldest Baptist denomination in America. As the institution developed, it adopted Andover's curricular pattern and shared the same theological tradition of loyalty to the evangelical Gospel and zeal for its dissemination.

In November 2015, ANTS announced that it would sell its campus and relocate to Yale Divinity School, after a presence of 190 years on that site.^[4]

Prior to the founding of Andover and Newton, the model for the training of clergy was based on an undergraduate degree (actually the basis for the founding of most of the early colleges in the United States). The graduate model and the three year curriculum with a resident student body and resident faculty pioneered at Andover and Newton has become the standard for almost all of the 140 Protestant theological schools in the country.

Reflecting that zeal, the modern missionary movement began in this country through a group of Andover students known as the Brethren. Both Andover and Newton quickly assumed leadership in the modern mission movement, drawing the two schools into close association of people and ideas. Graduates such as Luther Rice and Hiram Bingham pioneered in Christian missions around the world. Adoniram Judson, an 1810 Andover alumnus, is best known for his work in Burma, where he translated the Bible into Burmese and produced the first Burmese-English dictionary.

Alumni of Andover Theological Seminary include the following notables, listed in order of their last year at the Seminary.

• Paul Monroe, ed. (1911), "Andover Theological Seminary", Cyclopedia of Education, vol. 1, New York: Macmillan, hdl:2027/uc2.ark:/13960/t1xd15h17 – via HathiTrust

• Andover-Harvard Library Mission and History
• Andover Newton Seminary at Yale