The Minimax Theorem is a fundamental principle in game theory, particularly in zero-sum games, where one player's gain is another's loss. It states that in such games, there exists a strategy for each player that minimizes their maximum possible loss. This means that players can choose strategies that ensure the best possible outcome, even in the worst-case scenario. The theorem was first proven by John von Neumann in the 1920s and has since become a cornerstone of strategic decision-making. It provides a framework for analyzing competitive situations, helping players to make rational choices based on their opponents' potential actions.