  We study the effect of a perpendicular magnetic field on the electronic
structure and charge transport of a monolayer MoS$_2$ nanoribbon at zero
temperature. We particularly explore the induced valley Zeeman effect through
the coupling between the magnetic field, $B$, and the orbital magnetic moment.
We show that the effective two-band Hamiltonian provides a mismatch between the
valley Zeeman coupling in the conduction and valence bands due to the effective
mass asymmetry and it is proportional to $B^2$ similar to the diamagnetic shift
of exciton binding energies. However, the dominant term which evolves with $B$
linearly, originates from the multi-orbital and multi-band structures of the
system. Besides, we investigate the transport properties of the system by
calculating the spin-valley resolved conductance and show that, in a low-hole
doped case, the transport channels at the edge are chiral for one of the spin
components. This leads to a localization of the non-chiral spin component in
the presence of disorder and thus provides a spin-valley polarized transport
induced by disorder.
