We formulate non-Hermitian Landau levels in two-dimensional systems under a complex perpendicular magnetic field. In the symmetric gauge, we derive their discretely spaced, highly degenerate complex spectra and biorthogonal eigenstates. In addition we derive analogous results in the Landau gauge and clarify the role of non-unitary gauge transformations. We find that while normalizable eigenstates exist for both gauges for $Re(B)>0$, they are not always related by such a gauge transformation. A non-Hermitian Harper-Hofstadter lattice model confirms the continuum theory and reveals Gaussian wave packet dynamics governed by semiclassical equations with a complex Lorentz force, pointing to possible experimental realizations of complex magnetic fields in mechanical metamaterials or ultracold atom gases.