  Charged gauge boson pair production at the Large Hadron Collider allows
detailed probes of the fundamental structure of electroweak interactions. We
present precise theoretical predictions for on-shell $W^+W^-$ production that
include, for the first time, QCD effects up to next-to-next-to-leading order in
perturbation theory. As compared to next-to-leading order, the inclusive
$W^+W^-$ cross section is enhanced by 9% at 7 TeV and 12% at 14 TeV. The
residual perturbative uncertainty is at the 3% level. The severe contamination
of the $W^+W^-$ cross section due to top-quark resonances is discussed in
detail. Comparing different definitions of top-free $W^+W^-$ production in the
four and five flavour number schemes, we demonstrate that top-quark resonances
can be separated from the inclusive $W^+W^-$ cross section without significant
loss of theoretical precision.
