A general theory is developed for the equilibrium structure of dense polymer melts. This theory is based on an integral equation approach developed by Chandler and co-workers for molecular liquids. We are able to construct a tractable formalism for the polymer problem by employing the fact that a polymer molecule in a melt is ideal. This leads to a set of integral equations for the intermolecular radial distribution functions. In the case of a polymer ring, this set reduces to a single integral equation, which we have solved numerically for the case of Gaussian intramolecular statistics with repeat units interacting via hard-core repulsions. From this solution we obtained the radial distribution function, structure factor, and compressibility as functions of liquid de,nsity and degree of polymerization. Unlike the random phase approximation (RPA) approach of de Gennes, the present theory allows for density fluctuations. These density fluctuations, which decay on a length scale comparable to a few monomer units, are crucial for the calculation of the structure factor and thermodynamic properties such as the equation of state of the polymer fluid. Generalizations of the present theory to include linear chains, chain stiffness effects, and attractive interactions are possible.