A novel definition for quantum privacy based on hypothesis testing is presented. This privacy notion possesses an operational interpretation based on the false positive and negative rates of adversaries attempting to distinguish among private categories to which quantum states belong using arbitrary measurements. Important properties of post processing and composition are established. The relationship between privacy against hypothesis-testing adversaries and quantum differential privacy are then examined. This enables analysis of hypothesis testing under differential privacy and in noisy quantum systems. It also provides an operational interpretation for quantum differential privacy.