The objective of this article is to develop a control mechanism that can suppress the ongoing transient instability in a power system through the continuous delivery of corrective actions. The continuous delivery of corrective actions basically refers to performing multiple adjustments in series until the transient instability is completely healed. The motivation behind the particular work arises from the observation that exercising the corrective action merely once may not always be sufficient to restore the stability of the system. In order to enable the continuous delivery of corrective actions, a macrolevel dynamic assessment approach is taken instead of the conventional and microlevel static coherency assessment. The macrolevel coherency assessment is to be carried out based upon real-time snapshots of system quantities for the on-spot identification of generator groups that have grossly lost synchronism with one another. A complete transient instability mitigation program is developed with due application of the macrocoherency assessment in delivering continuous corrective actions. In order to ensure almost instantaneous computation of coherent generator groups, a novel clustering algorithm is also developed. Corrective actions are delivered in the form of generator rejection and load curtailment. Extensive verification of the proposed methodology is carried out by means of real-time software-in-loop simulations. © 2007-2012 IEEE.