The linear and nonlinear distortion and breakup of three-dimensional swirling or nonswirling annular and swirling conical thin inviscid liquid films are analyzed by means of a reduced-dimension approach. The films are unbounded in the downstream direction and discharge from an annular slit nozzle or atomizer into a gas of negligible density at negligible gravity, conditions. Nonlinear numerical simulations describe the distortion of modulated, initially undisturbed films up to the time when film rupture first occurs. Linear and nonlinear solutions are presented and discussed for various configurations and with either dilational or sinuous three-dimensional modulations imposed on the films at the nozzle exit. Nonlinear growth rates can be signicantly larger than those predicted by linear theory. Initially, axisymmetric disturbances remain axisymmetric and fluctuations in the circumferential direction generated by numerical error are not amplfied for the considered cases. Overall,film topology at the time offilm rupture suggests that single dilational or sinuous oblique waves will result in spiraling filaments detaching from the continuous film. Combination of clockwise and counterclockwise traveling dilational waves results in an approximately rectangular array of larger ligaments interspaced by thin fluid films indicating subsequent cellular-type breakup for both annular and conical configurations. Results for similar sinuous-mode modulations suggest film disintegration via shedding of continuous annular rings from swirling annular films and filament shedding from swirling conical films.