The existence of nonsymmetric generalized half-band lowpass and highpass FIR filters with maximally flat magnitude and group delay characteristics is proved. Like their linear-phase counterparts, approximately half of the impulse response coefficients of these generalized half-band filters are exactly zero. The magnitude response of the filters is not a monotone function in general. However, the filters can be designed to yield improved magnitude response characteristics compared to the linear-phase maximally flat filters. A closed-form formula for the transfer function of the filters is also derived using Bernstein polynomials. The filters may find applications in multirate and wavelet signal processing.