The Union Theological Seminary in the City of New York (often shortened to UTS or Union) is a private, ecumenical, liberal Christian seminary in Morningside Heights, Manhattan, New York City. It has been affiliated with Columbia University since 1928.

Presently, Columbia University lists UTS among its affiliate schools, along with the Columbia-degree conferring Barnard College and Teachers College. Beginning in 1928 and continuing until an indeterminate juncture, UTS "[had] the status of a [Columbia] University faculty in the educational system of the University through representation" on the now-defunct University Council. In 1964, UTS also established an affiliation with the neighboring Jewish Theological Seminary of America. Despite its affiliation with Columbia University, UTS has remained an independent institution with its own administration, degrees and Board of Trustees. UTS confers the following degrees: Master of Divinity (MDiv), Master of Divinity & Social Work dual degree (MDSW), Master of Arts in religion (MAR), Master of Arts in Social Justice (MASJ), Master of Sacred Theology (STM), Doctor of Ministry (DMin), and Doctor of Philosophy (PhD).

UTS is the oldest independent seminary in the United States and has long been known as a bastion of progressive Christian scholarship, with a number of prominent thinkers among its faculty or alumni. It was founded in 1836 by members of the Presbyterian Church in the USA, but was open to students of all denominations. In 1893, UTS rescinded the right of the General Assembly of the Presbyterian Church to veto faculty appointments, thus becoming fully independent. In the 20th century, Union became a center of liberal Christianity. It served as the birthplace of the Black theology, womanist theology, and other theological movements. It houses the Burke Library at Union Theological Seminary, one of the largest theological libraries in the Western Hemisphere.