Johann Heinrich Christoph Willibald Beyschlag (5 September 1823 – 25 November 1900 in Halle an der Saale) was a German theologian from Frankfurt am Main.
He studied theology at the Universities of Bonn and Berlin, afterwards serving as an assistant pastor in Koblenz (1849), then as a pastor in Trier (1850). During the following year, Beyschlag began working as a religious instructor in Mainz. In 1856 he became a court preacher in Karlsruhe, and four years later he was appointed a professor of practical theology and New Testament exegesis at the University of Halle.
Beyschlag was the leader of the Evangelical Mittelpartei ("Middle Party"), and in 1876, with Albrecht Wolters, founded the Deutsch-evangelischen Blätter (a publication of the Mittelpartei in the Kirche der Altpreußischen Union). Because of the combatative nature of the magazine, he was once sued for libel. Also, he was a primary catalyst in the founding of the Evangelische Bund (Protestant Confederation) — he believed that only in unity could German Protestantism find strength.
He was a leading supporter of the Vermittlungstheologie and was opposed to Chalcedonian Christology. Also, he stood for the rights of the laity, and believed in the autonomy of the church, leading him to be in favor of separation of church and state. Beyschlag was viewed as an antagonist of the Roman Catholic Church and a sharp critic of Ultramontanism.