We provide a detailed description of the CHIMERA code, a code developed to model core-collapse supernovae in multiple dimensions. Core-collapse supernovae are extremely important astrophysical events for multiple reasons, but the explosion mechanism seems to involve a complex interplay of radiation-hydrodynamics, fluid instabilities, weak interaction rates, and nuclear physics, and is still obscure. CHIMERA, by incorporating realistic neutrino interactions, detailed neutrino transport, a nuclear reaction network, and other refinements, can be used to study the role of hydrodynamic instabilities, neutrino radiation, and a variety of input physics in the explosion mechanism itself. It can also be used in core-collapse simulations to compute observables such as neutrino signatures, gravitational radiation, and the products of nucleosynthesis. The code contains modules for the equations of state, multidimensional compressible hydrodynamics, a variety of neutrino interactions, neutrino transport, nuclear reactions, and to provide data for post-processing observables such as the products of nucleosynthesis and gravitational radiation. CHIMERA is an evolving code, being updated periodically with improved input physics and numerical refinements. We detail here the current version of the code, from which future improvements can be then described as needed.