Abstract: Interconnected power grids throughout the world are very reliable but occasionally suffer massive blackouts with multibillion dollar costs to society. Cascading failures present severe threats to power grid reliability, and thus reducing their likelihood, mitigation and prevention is of significant importance. This paper is one in a series presented by Cascading Failures Task Force, under the IEEE PES Computer Analytical Methods Subcommittee (CAMS) with primary focus on mitigation and prevention of cascading outages. The paper presents the basic methodologies for mitigation, summarizes currently deployed special protection schemes, and lists cases of successful and unsuccessful mitigation of cascading outages and lessons learned. Future developments and challenges in the area of mitigating cascading outages are also discussed.