This paper focuses on the event-based distributed robust leaderless synchronization control for multiple Euler-Lagrange systems with directed communication topology that contains a directed spanning tree. Update frequency of the system is reduced by taking advantages of the event-triggered approach, which can help extend the service life of the controller. Robust control theory is employed to guarantee the synchronization stability of the networked Euler-Lagrange systems when unmodeled dynamics occur. The cost on the distributed synchronization protocol design can be saved due to the relaxation of the requirement on relative velocity measurements. Furthermore, our results are more practical because unknown disturbance is taken into consideration. In addition, it can be rigorously analyzed that each agent can exclude the undesired Zeno behavior. Some simulation examples are provided in the end to demonstrate the effectiveness of the proposed event-based distributed robust control algorithm.In practice, it is essential for the systems to be equipped with a better communication capability to obtain the accurate relative velocity information, which may raise communication burden and cost much computing resource. There have been some recent studies that aim to remove the requirement on relative velocity information from the control laws; here, we just list some of the most relevant papers as examples. Both containment control and leaderless synchronization control problems were addressed under directed networks by Mei et al. 10 Sliding mode estimators, distributed observers, and controllers were designed in the work of Yang et al 11 to solve the tracking control problem with a dynamic leader over directed graphs. A novel distributed observer, which is compatible for different control schemes with or without structure uncertainties, was introduced by Zhang et al 12 to deal with the leaderless synchronization control problem under undirected networks. Furthermore, distributed finite-time tracking protocols were proposed by Chen 7 and Zhao et al 13 under the assumptions that there exists a directed spanning tree rooted at the dynamic leader and the subgraph among followers are directed and undirected, respectively. Note that the above results all have employed an adaptive control scheme. However, it should be stressed that a plant that contains unmodeled dynamics may yield instability in practical designs by applying adaptive control theory, which implies that it is difficult to achieve the desirable coordination performance. 14,15 On this account, distributed control protocols were developed to cope with the synchronization problem from the standpoint of robust control mechanism in the works of Liu et al, 16,17 but they only guarantee the uniform ultimate boundedness of the synchronization errors and the communication networks are supposed to be strongly connected, which is a more restrictive condition.In recent years, event-triggered control, which plays a significant role in reducing communication frequency and/or con...