The Minimax Theorem is a fundamental principle in game theory, formulated by mathematician John von Neumann. It states that in a zero-sum game, where one player's gain is another's loss, there exists a strategy that minimizes the maximum possible loss. This means that players can determine their optimal strategies by considering the worst-case scenarios. In practical terms, the theorem assures that both players can achieve a stable outcome, known as a Nash Equilibrium, where neither player can benefit by changing their strategy unilaterally. This concept is widely applied in economics, political science, and artificial intelligence to analyze competitive situations.