This Article will examine the concept of immutability as it has been used in equal protection jurisprudence, particularly in the context of the gay rights movement. As a traditional matter, immutability was viewed as a doctrine that limited suspect and quasi-suspect classification status to those groups whose identities were fixed in some visible, often biological fashion. This narrow understanding of immutability served a purpose: it limited suspect or quasi-suspect status to those groups of individuals who were not at fault in some way for the subordinate condition in which they existed. Since the decisions in In re Marriage Cases, Kerrigan v. Commissioner of Public Health, and Varnum v. Brien, the concept of immutability has undergone a significant change: immutable characteristics are no longer limited to those traits that a person cannot change, but also include characteristics that a person should not have to change. This new understanding of immutability expands the definition of the concept, but it also accomplishes two important goals: (1) it moves past a fault-based model of immutability that generally seeks to exclude from protection groups whose moral culpability or personal responsibility are the cause of their condition, and (2) it moves toward an autonomy-based model of immutability premised on a respect for human dignity that protects critical constituitive aspects of personhood, which allows courts to offer heightened-scrutiny protection to groups whose public identities are often not obvious.