Donald Macpherson Baillie (5 November 1887 – 31 October 1954) was a Scottish theologian, ecumenist, and parish minister.
Baillie was ordained in 1918. Before his ordination he had worked an assistant in North Morningside Church, Edinburgh and the YMCA in France and at St. Boswell's Church in Edinburgh. After his ordination, he served as the minister of Bervie United Free Church from 1918-1923, followed by St. John's, Cupar until 1930 and then at St. Columba's, Kilmacolm until 1934. This led to his appointment as a professor of divinity at St Mary's College, University of St Andrews, where he spent the remainder of his life.
In 1935 he became Professor of Systematic Theology at the University of St Andrews, where he had been Additional examiner for the BD degree in Divinity and Ecclesiastical History from 1921-1924, and which had awarded him an Honorary DD in 1933. Other academic positions included External Examiner for the BD in Divinity at the University of Edinburgh from 1933, Forwood lecturer in the Philosophy of Religion at the University of Liverpool, 1947, and Moore lecturer at the San Francisco Theological Seminary, 1952. or 1946.
His more famous work was God was in Christ (1948), which explored the paradox of grace, and applied it to incarnational theology. The book went through five printings, including a separate German edition. He was still in post of Professor of Systematic Theology at the time of his death.