The optimal operation of multi-microgrids (MMGs) can be achieved by interconnection of them for power exchange between them and by reducing the total operation costs of different types of renewable energy resources (RERs) in MMGs. Therefore, solving the economic dispatch (ED) problem becomes one of the main challenges for the optimal operation of RERs by finding the optimal scheduling of these sources. This paper presents a procedure based on the marine predator optimizer (MPO) algorithm for solving the ED problem in MMGs. The minimization of total operating costs of RERs and battery energy storage (BES) is considered an objective function (OF) while satisfying the system constraints. The proposed algorithm is applied to two-microgrid systems connected together for solving the ED problem. The numerical results obtained for separate operation of MGs and MMGs using the proposed MPO are compared with other techniques such as jellyfish search (JS), particle swarm optimization (PSO), and differential evaluation algorithm (DEA) to prove the robustness of the proposed MPO for the economical operation of the MMGs.