In this paper, a new planar monopole antenna for multiband applications is proposed. The antenna structure operates at five operating frequencies at 2.88 GHz, 7.58 GHz, 9.88 GHz, 11.59 GHz and 13.78 GHz which covers different communication frequency ranges. The proposed antenna consists of a quasi-modified rectangular radiating patch with a partial ground plane and two parasitic elements (open-loop-ring resonators) to serve as coupling-bridges. A stepped cut at lower corners of the radiating patch and the partial ground plane are used, to achieve the multiband features. The proposed antenna is manufactured on the Rogers RO 3010 substrate and is simulated and optimized using High Frequency Simulation System (HFSS). The antenna topology possesses an area of 41.04 x 29.98 x 1.6 mm 3. The measured results demonstrate that, the candidate antenna has impedance bandwidths for-10 dB return loss and operates from 2.68-3.03 GHz, 7.33-7.84 GHz, from 9.66-10.03 GHz, from 11.46-11.78 GHz and from 13.69-13.88 which meet the requirements of the wireless local area network (WLAN), worldwide interoperability for microwave access (WiMAX), C-(Uplink), X-(Uplink) band and Ku-(Uplink) band applications. Acceptable agreement is obtained between measurement and simulation results. Experimental results show that the antenna is successfully simulated and measured, and the tri-band antenna can be achieved by adjusting the lengths of the three elements and gives good gains across all the operation bands.