Erhard Weigel (1625-1699), mathematician from Jena, developed within the context of his efforts for a mathematically oriented universal science and for a methodologically exact natural theology also a mathematical proof of God, which should prove God’s existence irrefutably and with the highest degree of certainty. Leibniz, as is known a disciple of Weigel himself, was already acquainted with the proof ’s earliest drafts from the 1670’s on and referred to almost all of Weigel’s publications on the proof of God in (...) his writings, which shows his never ceasing interest on this topic. The article presents the rationale of Weigel’s proof of God as well as the central aspects of Leibniz’s in part assenting while also in part critical considerations to it and gives an outlook on the importance of the topic for Leibniz’s own development. (shrink)