This paper, for the first time, fully characterizes the human body as a monopole antenna in the frequency range of 10 -110 MHz, which contains the resonance frequency of the human body. The human body is represented by an equivalent cylindrical monopole antenna grounded on a highly conductive ground plane that is analysed based on the three-term approximation method. The reflection coefficient is measured using a human subject as a monopole antenna. Measurement results show that the theoretical predictions are in reasonable agreement. It is found that the human body resonates between 40 -60 MHz depending on the posture of the body when it is fed by a 50 Ω impedance system at the base of the foot. A minimum reflection coefficient of -12 dB is measured that demonstrates that the human body can be potentially used as an antenna. Theoretically, it is predicted that the human body can be an efficient antenna with a maximum radiation efficiency reaching up to 70 %, which is supported by measurement results found in the literature.