A nozzle for a plasma arc torch has a longitudinal nozzle axis, a nozzle orifice with a generally cylindrical orifice sidewall centered on the nozzle axis, and an orifice inlet that is formed as a surface of rotation about the nozzle axis; a gas-directing surface may also be provided. The orifice inlet has a variably-curved surface generated by rotating a variably-curved element about the nozzle axis, where the variably-curved element can be a portion of an ellipse, parabola, or hyperbola, and can join to the orifice sidewall and to the gas-directing surface, if provided. Both the orifice sidewall and the gas directing surface can each join the variably-curved element in a substantially tangential manner. Using an elliptical contour for the orifice inlet was found to increase stability for the plasma arc, providing improved cut quality and faster cutting speed for the torch.