  We propose a topological soliton or instanton solution with nonzero Hopf
invariant to the 3+1D non-Abelian gauge theory coupled with scalar fields. This
solution, which we call Hopf soliton, represents a spacetime event that makes a
$2\pi$ rotation of the monopole. Although the action of this Hopf soliton is
logarithmically divergent, it may still give relevant contributions in a
finite-sized system. Since the Chern-Simons term for the unbroken $U(1)$ gauge
field may appear in the low energy effective theory, the Hopf soliton may
possibly generate fractional statistics for the monopoles.
