A simple and compact microstrip line -fed ultrawideband planar monopole antenna with single band-notch characteristics is presented. Wide impedance bandwidth is achieved by inserting two rectangular slots on both sides of the microstrip feed line on the ground plane. Band notching is achieved by embedding a half wavelength C shaped slot on the radiator. The antenna is investigated numerically and validated experimentally for impedance matching, frequency notch characteristics and radiation performance. The designed antenna has a compact size of 18 × 19 mm2 and operates over the frequency band between 3.1-12 GHz for VSWR < 2 while demonstrating band rejection performance in the frequency band of 5 to 6 GHz. The antenna exhibits omni directional characteristics with average gain of 2.26 dB. © 2005 - 2012 JATIT & LLS. All rights reserved.