This document describes the design and analysis of a rectangular horn antenna for WiFi applications at 5.5 GHz. The antenna was designed using CST simulation software. Simulation results showed the antenna had a return loss of -18 dB, a VSWR of 1.25, and a maximum gain of 12.1 dB at 5.5 GHz. The antenna's beamwidth was calculated to be 22.59 degrees vertically and 31.09 degrees horizontally. The rectangular horn antenna was found to effectively transmit signals for WiFi applications between 5.25-5.75 GHz with high gain and directivity.