A low-profile, tri-band, wide slot antenna for the Wireless Local Area Network (WLAN) and World-Wide Interoperability for Microwave Access (WiMAX) applications is proposed in this article. The surface dimension of the proposed planar antenna is 0.32λ Â 0.32λ mm 2 (lowest operating frequency). The antenna structure consists of a wide slot which is formed by carefully etching out the square and circular shapes from the basic patch antenna. The standard cost-effective FR-4 substrate with a thickness of 1.6 mm is used for the fabrication of the prototype. Tri-band resonance at 2.4, 3.5, and 5.5 GHz is achieved with the peak gain of 3.33, 1.12, and 1.37 dBi, respectively. The impedance bandwidth at three resonant peaks is 15.36%, 11.7%, and 8.29% with Voltage Standing Wave Ratio (VSWR) well below the requirement of 1.5. Dipoleshaped radiation patterns, average gain > 1.96 dBi, and efficiency of 83% make the antenna commercially viable for use in WLAN and WiMAX devices.