In mathematics, the axiom of real determinacy (abbreviated as ADR) is an axiom in set theory. It states the following:
Consider infinite two-person games with perfect information. Then, every game of length ω where both players choose real numbers is determined, i.e., one of the two players has a winning strategy.
The axiom of real determinacy is a stronger version of the axiom of determinacy, which makes the same statement about games where both players choose integers; it is inconsistent with the axiom of choice. ADR also implies the existence of inner models with certain large cardinals.