  Quantum spin liquids have been at the forefront of correlated electron
research ever since their original proposal in 1973, and the realization that
they belong to the broader class of intrinsic topological orders, along with
the fractional quantum Hall states. According to received wisdom, quantum spin
liquids can arise in frustrated magnets with low spin $S$, where strong quantum
fluctuations act to destabilize conventional, magnetically ordered states. Here
we present a magnet that has a $Z_2$ quantum spin liquid ground state already
in the semiclassical, large-$S$ limit. The state has both topological and
symmetry related ground state degeneracy, and two types of gaps, a `magnetic
flux' gap that scales linearly with $S$ and an `electric charge' gap that drops
exponentially in $S$. The magnet is described by the spin-$S$ version of the
spin-1/2 Kitaev honeycomb model, which has been the subject of intense studies
in correlated electron systems with strong spin-orbit coupling, and in optical
lattice realizations with ultracold atoms. The results apply to both integer
and half-integer spins.
