This document describes the design and simulation of a microstrip patch antenna in Ansoft HFSS. It discusses the basic components of a microstrip patch antenna including the radiating patch, dielectric substrate and ground plane. It then covers the simulation process in HFSS including defining the geometry, materials, boundary conditions, excitation source and frequency sweep setup. The document concludes that a rectangular patch antenna was successfully designed and simulated in HFSS to operate at 2.55 GHz.