  We report direct measurements via angle-resolved photoemission spectroscopy
(ARPES) of the electronic dispersion of single-layer CoO$_2$. The Fermi contour
consists of a large hole pocket centered at the $\overline{\Gamma}$ point. To
interpret the ARPES results, we use density functional theory (DFT) in
combination with the multi-orbital Gutzwiller Approximation (DFT+GA), basing
our calculations on crystalline structure parameters derived from x-ray
photoelectron diffraction and low-energy electron diffraction. Our calculations
are in good agreement with the measured dispersion. We conclude that the
material is a moderately correlated metal. We also discuss substrate effects,
and the influence of hydroxylation on the CoO$_2$ single-layer electronic
structure.
