Abstract: Full-scale operation of the ITER experiment will produce plasma thermal energy and releasable magnetic energy on the order of hundreds of mega-Joules. Unplanned disruptions to these discharges will be capable of causing significant material damage to plasma-facing components and electrically conducting structures. As such, the susceptibility to disruptions poses the greatest challenge for the tokamak as a fusion reactor concept. In this presentation, operational limits and the typical sequence of dynamics during disruptions are reviewed, as is the physics behind localized heat deposition, electromechanical forcing, and runaway electron (RE) generation. Extended-magnetohydrodynamic (MHD) numerical simulations provide insight into the physics of tokamak disruptions. Results computed with the NIMROD code (nimrodteam.org) describe profile relaxation and surface-force densities during asymmetric vertical displacement. Other simulations show the importance of MHD for mitigation with massive gas injection and shattered pellet injection. The confinement of REs and their influence on MHD is also considered.