The document describes a tunable ultra-wideband terahertz antenna based on a graphene fractal artificial magnetic conductor. The antenna consists of a bowtie patch mounted above an array of 15x15 graphene patches in a fractal shape. The resonance frequency and bandwidth of the antenna can be tuned by varying the applied voltage, which changes the chemical potential of the graphene. Simulation results show that both the resonance frequency and bandwidth increase when the chemical potential is increased from 0.4 eV to 1 eV. The fractal shape of the graphene patches provides a multiband response with multiple resonance frequencies. The antenna achieves wide bandwidths between 1.8-2.2 THz and 2.75-5 THz when the chemical