A true random number generator based on the magnetization backhopping process in nano-ring magnetic tunnel junctions is demonstrated in this work. The impact of environmental temperature (T) and current pulse width (τ) on backhopping is investigated statistically by experiments, micromagnetic simulations, and theoretical analysis. The backhopping probability increases at high T and wide τ, as explained by the combined effect of thermal fluctuation and spin-transfer-torque noise. The magnetoresistance at backhopping is randomly distributed over a large operational current range. This manifestation of backhopping in magnetic tunnel junctions can be used as the basic unit of a true random number generator.