There is high probability for the long-term crustal accumulation of methane and carbon dioxide on Mars. These gases can arise from a variety of processes, including deep biosphere activity and abiotic mechanisms, or, like water, they could exist as remnants of planetary formation and by-products of internal differentiation. CH4 and CO2 would tend to rise buoyantly toward the planet's surface, condensing with water under appropriate conditions of temperature and pressure to form gas hydrate. Gas hydrates are a class of materials created when gas molecules are trapped within a crystalline lattice of water-ice. The hydrate stability fields of both CH4 and CO2 encompass a portion of the Martian crust that extends from within the water-ice cryosphere, from a depth as shallow as ~10--20 m to as great as a kilometer or more below the base of the Martian cryosphere. The presence and distribution of methane and carbon dioxide hydrates may be of critical importance in understanding the geomorphic evolution of Mars and the geophysical identification of water and other volatiles stored in the hydrates. Of critical importance, Martian gas hydrates would ensure the availability of key in situ resources for sustaining future robotic and human exploration, and the eventual colonization, of Mars.