Walther Theodor Zimmerli (20 January 1907 – 4 December 1983) was a Swiss academic theologian in the Reformed tradition and an Old Testament scholar.
Zimmerli was active in the academic division of the Council of Europe, served on the board of the World Rectors' Conference and was in the senate of the Deutschen Forschungsgemeinschaft.
In 1949, Claus Westermann earned his doctoral degree in Zurich under Zimmerli for his dissertation "Das Loben Gottes in den Psalmen" ("Praise of God in the Psalms").
Zimmerli was a highly regarded and well known representative of his discipline and was therefore invited to be a guest professor at Yale University, granted many honorary doctorates (from Göttingen, Zurich, Strasbourg and Edinburgh) and was the 1972 recipient of the Burkitt Medal of the British Academy.
Zimmerli's scholarship is embodied in his Grundriß der alttestamentlichen Theologie (Old Testament Theology in Outline), which has appeared in numerous editions since its first publication.