This work aims to evaluate the free vibration of deformable fluid-filled rectangular tanks in two dimensions. These tanks are surrounded by soil, and consequently, the soil-fluid-structure interaction is taken into account. Here, the fluid is supposed to be compressible, non-rotational, and non-viscous. And, the soil is presumed to be cohesive. Besides the analytical solution, the formulation using finite elements to solve the problem is presented. For validating the suggested analytical solution, several numerical examples are examined. Additionally, a sensitivity analysis is performed to examine how various parameters affect the fluid–structure-soil system\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'s natural frequencies and mode shapes. Findings have proven the correctness of the proposed solution.

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