We introduce the AGORA project , a comprehensive numerical study of well-resolved galaxies within the \Lambda CDM cosmology . Cosmological hydrodynamic simulations with force resolutions of \sim 100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth , star formation history , morphological transformation , and the cycle of baryons in and out of 8 galaxies with halo masses M _ { vir } \simeq 10 ^ { 10 } , 10 ^ { 11 } , 10 ^ { 12 } , and 10 ^ { 13 } { M _ { \odot } } at z = 0 and two different ( “ violent ” and “ quiescent ” ) assembly histories . The numerical techniques and implementations used in this project include the smoothed particle hydrodynamics codes Gadget and Gasoline , and the adaptive mesh refinement codes Art , Enzo , and Ramses . The codes will share common initial conditions and common astrophysics packages including UV background , metal-dependent radiative cooling , metal and energy yields of supernovae , and stellar initial mass function . These are described in detail in the present paper . Subgrid star formation and feedback prescriptions will be tuned to provide a realistic interstellar and circumgalactic medium using a non-cosmological disk galaxy simulation . Cosmological runs will be systematically compared with each other using a common analysis toolkit , and validated against observations to verify that the solutions are robust – i.e. , that the astrophysical assumptions are responsible for any success , rather than artifacts of particular implementations . The goals of the AGORA project are , broadly speaking , to raise the realism and predictive power of galaxy simulations and the understanding of the feedback processes that regulate galaxy “ metabolism. ” The initial conditions for the AGORA galaxies as well as simulation outputs at various epochs will be made publicly available to the community . The proof-of-concept dark matter-only test of the formation of a galactic halo with a z = 0 mass of M _ { vir } \simeq 1.7 \times 10 ^ { 11 } { M _ { \odot } } by 9 different versions of the participating codes is also presented to validate the infrastructure of the project .