An accurate line list for calcium oxide is presented covering transitions between all bound ro-vibronic levels from the five lowest electronic states. The ro-vibronic energies and corresponding wavefunctions were obtained by solving the fully coupled Schroedinger equation. Ab initio potential energy, spin-orbit, and electronic angular momentum curves were refined by fitting to the experimental frequencies and experimentally derived energies available in the literature. Using our refined model and high level ab initio electric dipole moments reported previously accurate ro-vibronic energies and Einstein A coefficients were computed. Our work is the first fully coupled description of this system. Our line list is the most complete catalogue of spectroscopic transitions available for CaO and is applicable for temperatures up to at least 5000 K. CaO has yet to be observed astronomically but its transitions are characterised by being particularly strong which should facilitate its detection. The CaO line list is made available in an electronic form as supplementary data to this article and at www.exomol.com.