Abstract <p>Throughout the exploration of the Solar System using spacecraft, Mercury has received less attention compared to Venus and Mars as the inner planet due to the inherent challenges of designing efficient trajectories in terms of both time and energy. A mission to Mercury requires a substantial reduction in the spacecraft’s heliocentric velocity, enabling its transfer into the inner Solar System. This trajectory optimization problem remains complex due to the interplay between gravitational influences, spacecraft constraints, and mission objectives. This study focuses on the development and optimization of interplanetary trajectories that minimize the total characteristic velocity (Δ<i>v</i>) while meeting constraints on flight duration and flyby altitudes during gravity assist maneuvers. The proposed methodology incorporates gravity assist maneuvers near Earth, Venus, and Mercury, combined with deep space maneuvers (DSMs) for phasing and energy optimization. Two new trajectory designs are presented as examples, demonstrating improvements over traditional approaches by reducing mission duration by one year without exceeding the characteristic velocity budget of NASA’s MESSENGER mission. These results underscore the potential for further improvements in trajectory optimization through refined algorithms and expanded mission constraints. This work highlights the importance of integrating advanced computational techniques with modern propulsion technologies to enhance the feasibility of Mercury exploration. By addressing key challenges in mission design, it contributes to a growing framework for more efficient and scientifically productive missions to the innermost planet of the Solar System.</p>