<p>Spin torque nano-oscillators have received continuously increasing attention due to their rich dynamics and potential applications. Here, we propose a spin torque nano-oscillator based on a ferrimagnetic skyrmion lattice, where the weak Magnus forces together with intriguing skyrmion-skyrmion interactions allow current-driven skyrmions to oscillate at terahertz frequencies. Through micromagnetic simulations, we demonstrate that a small current injection area results in identical motion orbits for the oscillating skyrmions, while a large injection area yields distinct or even chaotic trajectories. We analyze the transition between identical and distinct orbits using the Thiele equation, which also explains the parameter dependence of the oscillator frequency. In addition, synchronized oscillation signals emitted from a single oscillator are demonstrated. Our results not only reveal the high-frequency oscillation dynamics of ferrimagnetic skyrmions, but also pave the way for developing skyrmion-based oscillators.</p>