This paper presents the modelling and analysis of graphene based monopole antennas for Terahertz (THz) Band communications in micro-networks. Graphene is used as a conductor for radiating patch and ground in monopole antenna structures. Polyimide of thickness 143 μm is used as substrate with relative permittivity of 3.5. Two types of antennas were modelled; one is narrowband resonating at 0.1 THz and the other is wideband operating in 0.030-0.117 THz band. The second antenna has broader impedance bandwidth (>10\%) in the band of operation. © 2018 IEEE.