Following the advent of the Internet of Things (IoT), users and their devices transmit sensitive data over the Internet. For the Web, Let’s Encrypt offers a usable foundation to safeguard such data by straightforwardly issuing certificates. However, its approach is not directly applicable to the IoT as deployments lack a (dedicated) domain or miss essentials to prove domain ownership required for Let’s Encrypt. Thus, a usable approach to secure IoT deployments by properly authenticating IoT devices is missing. To close this research gap, we propose LUA-IoT, our framework to Let’s Usably Authenticate the IoT. LUA-IoT enables autonomous certificate enrollment by orienting at the success story of Let’s Encrypt, seamlessly integrating in the setup process of modern IoT devices, and relying on process steps that users already know from other domains. In the end, LUA-IoT binds the authenticity of IoT deployments to a globally valid user identifier, e.g., an email address, that is included in certificates directly issued to the IoT deployments. We exemplarily implement LUA-IoT to show that it is realizable on commodity IoT hardware and conduct a small user study indicating that LUA-IoT indeed nudges users to safeguard their devices and data (transmissions).