In this talk er present the global dynamics of Rayleigh–Duffing oscillators. The bifurcation diagram includes pitchfork bifurcation, Hopf bifurcation, and heteroclinic bifurcation. Meanwhile, the global phase portraits in the Poincaré disc are given. The system has at most one limit cycle. Moreover, when the limit cycle exists, its corresponding parameter region lies between Hopf and heteroclinic loop bifurcation curves in the parametric space. In addition, the analytic properties of the heteroclinic loop bifurcation curve are also analyzed. Finally, a few numerical examples are presented to verify our theoretical results.