The Moore–Spiegel system is a nonlinear thermo-mechanical oscillator with displacement . The parameter is analogous to the Prandtl number times the Rayleigh number, while is analogous to the Prandtl number times the Taylor number. The system describes a fluid element oscillating vertically in a temperature gradient with a linear restoring force.

The equations of the system are: , , .

Along with the Lorenz system, the Moore–Spiegel system is one of the classical low-order dynamical systems that exhibits chaos.