MIT's 14.12 Economic Applications of Game Theory, taught by Ian Ball, turns in this session to markets that fall short of perfect competition. Ball works through models of monopoly and oligopoly, using oil production quotas and cell phone carriers as running examples to show how firms set prices when they have some control over the market rather than none. The lecture builds out the game-theoretic tools for comparing a market with a single dominant producer against one split among several rivals, tracing how the number of competitors changes pricing incentives and output decisions. Expect blackboard derivations and worked examples rather than slides, in the standard MIT OpenCourseWare lecture format, aimed at students who already have the basics of game theory and want to see it applied to industrial organization.