The paper describes a light-weight monopole planar antenna with a rectangular radiating patch and a slotted ground plane for WiMAX (Worldwide Interoperability for Microwave Access) applications. WiMAX is a wireless broadband communication technology based around the IEEE 802.16 that provides point-to-multipoint wireless networking system and high-speed data across a wide range. The antenna designed for the aforementioned applications shows operation at 2.5 (lower WiMAX) / 3.7, 4.5 (middle WiMAX) / 5.5 (upper WiMAX) GHz with total bandwidth of about 110 MHz / 150 MHz / 160 MHz / 120 MHz. With its appealing characteristics, the planar monopole patch antenna meets the requirements of low weight, low cost, less complex structure and standard pattern of omnidirectional radiation.