In this paper, a novel band-notched ultrawideband (UWB) monopole antenna with high notch-band-edge selectivity is proposed and demonstrated. The proposed antenna consists of a radiation patch and an embedded second-order bandstop filter. Using the same substrate area as a fundamental UWB antenna, a bandstop filter composed of a nonuniform short-circuited stub and coupled open-/short-circuited stub resonators, is designed into the fundamental antenna. A detail design procedure for the proposed antenna with a second-order maximally flat bandstop filter at 5.5 GHz is presented. As compared to the fundamental antenna, the proposed UWB antenna provides good notch-band suppression from 5.15 to 5.95 GHz, in which the normalized total radiated powers in the notch band are lower than -12 dB. Also, the proposed structure provides high band-edge selectivity and flat return loss in the notch band. The measured results, including the return loss and total radiated power, agree with the designed ones.