It is difficult to overstate the importance of identity in the digital age, as well as the importance of digitized information for identity. In order to advance security, liberty, and privacy in modern society, it is crucial to understand the nuances of what identity means and how it is used and abused. This article defines identity, covering both physical and virtual entities, which is relevant in diverse contexts such as forensic science, cybersecurity, and national security. This article concentrates on the relevance of identity in forensic science, and provides illustrative examples. Approaches and challenges to evaluating and expressing confidence in identity-related conclusions are discussed. Privacy issues are considered along with the rising risks of identity usurpation and impersonation. Relationships between identification of physical and virtual entities are addressed, including the weaknesses and strengths of digital information alone, and the benefits of combining multiple forensic disciplines when assessing identity. This article concludes with a consideration of the benefits for forensic science specifically, and society generally, to take a pluridisciplinary approach to establishing identity.