Based on the integral sliding mode control method, some theoretical criteria for the robust synchronization of multi-coupled general non-linear systems with external disturbances are presented, the ultimate error bounds are estimated simultaneously. Furthermore, as an application, the detailed analysis and conclusions are derived for a network of multi-coupled FitzHugh–Nagumo (FHN) systems with external disturbances. Finally, some numerical examples, with two or more coupled FHN systems, are given to illustrate the effectiveness of the proposed theoretical results.