"Mathematical Methods for Economic Theory 1" is a comprehensive textbook aimed at graduate-level students in economics, while also serving as a reference work for professionals in the field. The two volumes are designed to provide a careful and independent development of mathematical concepts that are essential for understanding economic theories. The first volume covers fundamental topics such as set theory, sequences and series, as well as continuous and semi-continuous functions. Additionally, it offers an introduction to general linear spaces and basic concepts of convexity, which are applied to economic applications. The second volume expands on these concepts with general topology and the theory of correspondences in topological spaces, including Banach spaces and topological vector spaces. The theorems discussed, such as the maximum theorem, fixed-point theorem, and selection theorem, are central to modern economic theory.