in general, self-identification refers to being able to identify yourself with a group, community or label.

In the context of transgender identities, it refers to the ability of individuals who are transgender to identify with their gender identity without the approval of the various legal and medical authorities, such as the ability to identify as a man or a woman (or indeed, the various agender or nonbinary identities) without approval, or the prerequisite of gender reassignment surgery; in much the same way one has the agency to define their sexuality without medical approval.

Self-identification in the transgender community has proved controversial and raised concerns amongst some people; but it has also become a rallying-cry amongst transphobic people who attempt to use it in an alarmist way by inventing extreme scenarios.