  We show that momentum operators of a topological soliton may not commute
among themselves when the soliton is associated with the second cohomology
$H^2$ of the target space. The commutation relation is proportional to the
winding number, taking a constant value within each topological sector. The
noncommutativity makes it impossible to specify the momentum of a topological
soliton, and induces a Magnus force.
