Geometric Patterns in Zoroastrian Texts and Shāhnāmeh

God has created the universe according to patterns which only some of them have been revealed to man. Among these patterns related to the form and function of creatures, geometric patterns and proportions are of great importance in terms of visual beauty and structural strength. The purpose of this descriptive-analytical study is to study the signs of geometric proportion in Zoroastrian texts and Shāhnāmeh. The type of proportion and the geometric shapes that are explicitly stated in these texts are examined and the following questions are answered: What is the type of geometric proportion mentioned in these texts? To what extent do these proportions correspond to their current meaning? The results of the research show that according to Zoroastrian texts and Shāhnāmeh, there are signs of using the geometric proportions of squares and circles in the first creatures of Ahura and in some man-made structures. These mythological proportions seem to be close to the classic concept of proportion, according to which if the spiritual aspect of a phenomenon is greater, its geometric shape will be closer to a circle. Also, when it comes to the physical world, the issue of geometric proportion of square is raised.