In this article, a novel miniaturized tri-band monopole antenna for WLAN/WiMAX applications is presented and investigated. The proposed antenna consists of a horizontal H-shaped patch, an L-shaped open end stub, and a deformed inverted T-shaped strip. The patch attached to the 50-Ω feed-line through a matching line can increase the bandwidth of the proposed antenna. The bandwidths under the condition of|S11|≤−10dB of the proposed antenna are 340MHz (2.4–2.74GHz), 340MHz(3.41–3.75GHz), and640MHz(5.24–5.88GHz), respectively, indicatingthisantennaissuitable for WLAN (2.45–2.4835, 5.16–5.35, and 5.725–5.85GHz) and WiMAX (2.5–2.69, 3.4–3.69, and 5.28– 5.85GHz) applications. The antenna is successfully simulated and measured. Experimental results show that the proposed antenna with compact size of 30×20×0.8mm3 has nearly omnidirectional radiation characteristics and stable gains across all the operating bands with a simple structure.