John Williamson Nevin (1803–1886) was an American theologian and professor. He studied at Princeton University and was a professor of biblical literature at Western Theological Seminary in Allegheny, Pennsylvania and an ordained minister in the Presbyterian Church. Well-versed in German, he studied contemporary German theologians, and eventually converted to the German Reformed Church, accepting a position at the Church’s seminary in Mercersburg, PA. He and his colleagues developed a conservative doctrinal position eventually labeled the “Mercersburg Theology.”