For strategic games, the Nash equilibrium concept is axiomatized using three properties: (i) if the difference between two games is 'strategically irrelevant', then their solutions are the same; (ii) if a player has a strategy with a constant payoff, this player need not settle for less in any solution of the game; (iii) if all players agree that a certain strategy profile is optimal, then this strategy profile is a solution of the game. (C) 2019 Elsevier Inc. All rights reserved.