The static tensile test is a standard method for determining the mechanical properties of materials, regardless of whether they are elastic, viscoelastic, or elastoplastic. For homogeneous isotropic materials, such as metals, uniaxial tensile tests are commonly used, whereas biaxial tensile testing is required for anisotropic materials. Tensile tests are performed using specimens whose shapes are defined by standards depending on the material being tested. Laboratory testing has shown that standardized specimens often fail outside the testing area, primarily because the maximum stress is not located in the homogeneous region of the testing section. This results in inaccurate tensile test outcomes. The objective of this paper is to design a test specimen for uniaxial and biaxial tensile testing with a geometry that ensures that the maximum stress during testing is evenly distributed over as large a homogeneous area as possible within the testing section. To determine the appropriate specimen geometry, structural optimization methods, including topology optimization and shape optimization, implemented in the Abaqus software, were employed. The introductory part of the paper presents the basics of uniaxial and biaxial tensile testing, literature results, and issues related to specimen geometries. The concept of structural optimization is then described, including its mathematical foundation. Shape optimization and topology optimization, as types of structural optimization used for specimen design optimization, are also elaborated. Following this, the validation of topology optimization was conducted using a literature example with known solutions to confirm the accuracy and reliability of the specified simulation parameters. The final two chapters present the optimization processes for various geometries of uniaxial and biaxial specimens. The results of these processes served as guidelines for designing optimal geometries of test specimens intended for tensile testing.