Arizona voters will decide Proposition 318 on November 3, 2026, a legislatively referred measure that would require schools and athletic associations to designate teams and private spaces such as restrooms and locker rooms based on biological sex recorded on original birth certificates. Republican lawmakers advanced the proposal after prior state restrictions faced litigation, with a June 2026 Supreme Court ruling supporting enforcement of similar biological-sex eligibility rules in other states. The 59.5% implied probability for passage reflects Arizona’s divided electorate on the issue, partisan referral patterns, and national trends favoring sex-based categories in school athletics, though outcomes remain sensitive to turnout and last-minute campaign developments in the final weeks before the election.