This lecture covers the nonlinear classical dynamics of an optomechanical system, including dynamical instability, mechanical limit cycles, synchronization, and chaos. The instructor introduces the optomechanical attractor diagram and encourages exploration using the Cavity Optomechanics Simulator. The power balance condition, phase space picture of limit cycles, synchronization phenomena, and pattern formation in oscillator arrays are discussed. The lecture concludes with a summary of key concepts and pointers to relevant literature.