Devices with 3D capabilities are quickly gaining in popularity. In this paper, we propose to bring authentication into the third dimension. We define the concept of a 3D authentication scheme based on physical and psychological advantages of 3D. We implement an example of 3D authentication: 3DPass, to demonstrate the superiority of the 3D approach. Our security analysis of 3DPass demonstrates that 3DPass can exceed the password space of an 8 character alphanumeric password with just 6 choices. Our user study finds that 3DPass has superior memorability versus traditional alphanumeric passwords: 98% vs 83% recall rates after one week. We find that passwords in our scheme can be entered in 21 seconds on average when used with the Oculus Rift. We find that using the Oculus Rift improves entry time compared to a traditional 2D display, despite having no impact on presence (the feeling of “being there”) or user preference.